So yeah..., I'm going to do a full oil swap some time next month, and I've been reading around about the oils.

I'm looking to get my car into the best shape possible (I never settle for cheap crap when it comes to the car). Any recommendations?

I need:
-Engine Oil
-Transmission Oil
-Limited Slip Differential Oil

RP Engine Oil
Redline Trans and Diff Fluid

RP Engine Oil
Redline Trans and Diff Fluid

Agreed, thats what I use.

I use Royal Purple for Everything. 5w30 engine, MaxGear 75w90 for Trans/Diff.

Question: Is Royal Purple synthetic? As much as I want the best for my car, I really don't want to go beyond "the book".

I read around, and the Royal Purple logo says "Synthetic Oil".

Also, is the Royal Purple XPR Racing Oil any different from the normal ones? I don't use methanol, nitrous, etc. etc., which the product description seems to suggest that the XPR is best for.

Racing oils are designed for the track, not city traffic, I read somewhere that they are too thin.

^^ they have different additive packs for totally different usages.......

Has nothing to do with viscosity...but more about how well they stand up to crap around town driving conditions.

Okay, a little change in my question:

What's the best NON-SYNTHETIC engine oil money can buy?

Okay, a little change in my question:

What's the best NON-SYNTHETIC engine oil money can buy?

The lines become blurred. The more you refine petroleum, the more you approach and then exceed the definition of "synthetic". Unless you're talking about "building" oil molecules out of individual carbon and hydrogen atoms with nanotech, all of the processes start out with some kind of hydrocarbon feedstock. Some of the fancier ones start out with natural gas, iirc..

You've got the right forum, some searching will give you hours of reading if you're inclined. If you really want to go off the deep end about oil, visit "bobistheoilguy.com". Have fun! :)

Huh what? Best oil money can buy ?

I use Mazola for cooking, Betorili (Spelling) for salad, and maybe some peanut oil for frying.

j/k :P

Well, any name brand oil should do, Synthetic or not. I will stay away from crap like *Autozone blah blah blah* tho. Yeah they're name brand, but not some name brand that I can trust. They're selling them for like 1.25 a quart O_O

True Synthetic should use Group IV or V Base stock. Royal Purple use IV, and Redline use V. Some Synthetics like Castrol Syntec, are NOT true Synthetic, most of them are Group III Hydrocracked oil like Pennzoil. The ONLY "true" Full Synthetic in Castrol Syntec is the 0w30 one.

Castrol GTX is a pretty famouse non-synthetic oil that a lot of people use. but I would suggest to stay away from the 5w20. get at least something with 30 grade. Synthetic or not.

I have been using nothing but Synthetic for a long time. Yeah I got some *not real Synthetic* from Castrol, but I never use it on my car, I used them on my bro and father's car LOL, but I still mix them with some True Synthetic like RP and 0w30 Syntec. Im using the Syntec 0w30 right now. when my stock runs out (maybe another 5 oil change), then Im gonna start using Redline 5w40.

Okay, a little change in my question:

What's the best NON-SYNTHETIC engine oil money can buy?
CASTROL GTX

Having tried many different gear lubes, I always find myself coming back to the factory-type 75-90, usually Mobil1 synthetic. I have had trouble, even in the summer, with the "clinging-type" oils making my tranny synchros slow to spin up. The same phenom resulted in a stiff rear diff when I used RP. Engine oil? I am looking into some new stuff right now.

Castrol GTX is a pretty famouse non-synthetic oil that a lot of people use. but I would suggest to stay away from the 5w20. get at least something with 30 grade. Synthetic or not.


Thanks for the info.

But why stay away from 5w20 when the manual says explicitly to use 5w20?

Because 5-20 was spec'd so as to meet CAFE standards. I use 0-30 in the winter, 5-30 in the spring/fall, and 10-30 in the summer.

some people believe its too thin. i was running 10w-30 for a while and i didnt really notice a difference. some people even recommend 10w40.

since my dealerships change my oil i get 5w-20. also, i use nothing but castrol gtx. once my warranty runs out i'll be using a synthetic, probably 10w30 or 10w40. very important to let the engine properly warm up before you move the car if you go to a higher weight.

+1 for Castrol GTX

5w20 is the one Mazda officially wants us to use so it meets CAFE (http://en.wikipedia.org/wiki/Corporate_Average_Fuel_Economy). Supposedly it gives better fuel economy (but at what expense?!?!?) and is also given to other Ford vehicles in the US.

Other regions of the world recommend much heavier weight oils for the RX-8 (including 40W). 5W-30 has been used by lots of folks here and is the one to go for IMO.

The 5W-20 factory fill is only good for one thing... break-in and drain hahaha.. I drained it the 2nd day I got mine

Is there a well documented source that recommends 5w30? Seriously. This vehicle is my everything. If using the wrong oil leads to it going bust, I'll be SOL.

Is there a well documented source that recommends 5w30? Seriously. This vehicle is my everything. If using the wrong oil leads to it going bust, I'll be SOL.

Mazda told the rest of the world to use 30 weight oil, is that well document for you ?

and MOST rotary expert recommend heavier than 30, not sure if that counts.

Like I said above, if u ask me I'll tell u to go with at least 30, for me, I will go 40 as soon as my supply runs out.

Having tried many different gear lubes, I always find myself coming back to the factory-type 75-90, usually Mobil1 synthetic. I have had trouble, even in the summer, with the "clinging-type" oils making my tranny synchros slow to spin up. The same phenom resulted in a stiff rear diff when I used RP. Engine oil? I am looking into some new stuff right now.

So what do you use right now for Gear box and Rear Diff ?

I kinda want to try Redline 75w90NS for the tranny and the 75w90 for rear diff

nycgps, how many miles have you driven with 5w30?

nycgps, how many miles have you driven with 5w30?

about 33K miles.

Just think of it, the rest of the world never got any engine recall, only North America did, and we're the only one thats spec to use 5w20. Does that tell you something ?

So what do you use right now for Gear box and Rear Diff ?

I kinda want to try Redline 75w90NS for the tranny and the 75w90 for rear diff



Woa before you go and destroy your tranny, don't put that 75W90NS in there!

You should be using Redline MT90 / MTL.. personally I prefer a 50/50 mix of MT90 and MTL (MTL is too light and MT90 is a tad bit heavy for cold starts.. and the mix works.. they're designed to be mixed for an ideal application anyway).

Redline 75W90 for the rear diff is correct.

Is there a well documented source that recommends 5w30? Seriously. This vehicle is my everything. If using the wrong oil leads to it going bust, I'll be SOL.


Dude, allot of folks here love their 8s too. In my case, 4 years of anticipation, including immigrating to the US just to land a job, and having a strict savings regimen specifically to buy an 8 and keep it for life. 5W30 works.. really.

Woa before you go and destroy your tranny, don't put that 75W90NS in there!

You should be using Redline MT90 / MTL.. personally I prefer a 50/50 mix of MT90 and MTL (MTL is too light and MT90 is a tad bit heavy for cold starts.. and the mix works.. they're designed to be mixed for an ideal application anyway).

Redline 75W90 for the rear diff is correct.

why wont the NS stuff works in the tranny ? it does not contain the slippy stuff for differential. Better for Syncro isnt it ?

I just changed my gear oil yesterday with RP 75w90. For the Rear Diff, well, I dont have enough RP that time, so I put about a quart of 75w90 in there, then the rest is Mobil 1 75w90.

I thought about MT90 and MTL, and I want to try something different. Im gonna play with my new coilover settings tomorrow and will jack the car up most of the time, hmm I might as well just drain the RP tranny stuff and try some Redline MTL + MT90 sucker :)

IIRC, our tranny calls for GL4 spec oil. GL5 (which 75W90NS (http://redlineoil.carshopinc.com/product_info.php/products_id/45597/58304) is) will not work.

IIRC, our tranny calls for GL4 spec oil. GL5 (which 75W90NS (http://redlineoil.carshopinc.com/product_info.php/products_id/45597/58304) is) will not work.

Right, damn, I forgot about that ! lol ! I kept on thinking its the other way around (calls for GL5 instead of 4)

jesus ... lol

Ok, NS will not work. I just changed the oil so I guess Im just gonna wait a bit b4 I pour it out and use Redline MT90. Thx :)

Oh great, another expert :icon_no2: The Mazda RX-8 Manual Transmission (Y16M-D) Service Manual calls out 75W90 in either API Service Spec GL4 or GL5.

The issue is whether or not the oil has limited slip lube in it, which most standard gear oils do. The "NS" designation for Redline means it doesn't have limited slip lube added which isn't good for synchro engagement. This is why people using Royal Purple gear oil are having grinding synchro issues. If you insist on using Royal Purple you need to be using the Synchromax gear oil. If you want to use Redline my recommendation is MT-90 (a 75W90 GL4), 75W90NS (GL5), or 75W140NS (GL5). Racers can also use Shockproof Heavy.

Redline MTL isn't heavy enough. If you push it hard with this lube the trans will eventually have a catastrophic failure. I know, it cost me trans #2.

Is there a well documented source that recommends 5w30? Seriously. This vehicle is my everything. If using the wrong oil leads to it going bust, I'll be SOL.

Even if there was unanamous agreement here that 5w20 was the best weight, you would not do any harm using 5w30. There's a long standing car guy tradition of using one weight higher than the official recommendation. Tom McCahill always stood behind that principle. (Also using single weight non-detergent oil, but times were different back then.)

You might look up the thread on the disassembly of Expo1's engine for oil insights by some pretty knowledgable folks.

Whether you go dino or synthetic, 5w20 or 5w30, make sure that the specifications for each kind of oil match what the owner's manual says. There's a TSB on the rear end oil, giving an alternate if what's specified in the owner's manual isn't available.

Ken

Oh great, another expert :icon_no2: The Mazda RX-8 Manual Transmission (Y16M-D) Service Manual calls out 75W90 in either API Service Spec GL4 or GL5.

The issue is whether or not the oil has limited slip lube in it, which most standard gear oils do. The "NS" designation for Redline means it doesn't have limited slip lube added which isn't good for synchro engagement. This is why people using Royal Purple gear oil are having grinding synchro issues. If you insist on using Royal Purple you need to be using the Synchromax gear oil. If you want to use Redline my recommendation is MT-90 (a 75W90 GL4), 75W90NS (GL5), or 75W140NS (GL5). Racers can also use Shockproof Heavy.

Redline MTL isn't heavy enough. If you push it hard with this lube the trans will eventually have a catastrophic failure. I know, it cost me trans #2.


Sorry I didn't intend to come out as an expert.. I was bouncing all over the place while hunting for the proper tranny fluid too but my 2007 owner's manual (http://www.mazdausa.com/MusaWeb/pdf/manuals/2007_RX8_OM.pdf)
(page 375) states "API Service GL-4 (SAE 75W-90)". Anyway, I accede to your better understanding of our tranny :worship:

Oh great, another expert :icon_no2: The Mazda RX-8 Manual Transmission (Y16M-D) Service Manual calls out 75W90 in either API Service Spec GL4 or GL5.

The issue is whether or not the oil has limited slip lube in it, which most standard gear oils do. The "NS" designation for Redline means it doesn't have limited slip lube added which isn't good for synchro engagement. This is why people using Royal Purple gear oil are having grinding synchro issues. If you insist on using Royal Purple you need to be using the Synchromax gear oil. If you want to use Redline my recommendation is MT-90 (a 75W90 GL4), 75W90NS (GL5), or 75W140NS (GL5). Racers can also use Shockproof Heavy.

Redline MTL isn't heavy enough. If you push it hard with this lube the trans will eventually have a catastrophic failure. I know, it cost me trans #2.

so my brain in fact is functional ! Cuz last night I was like "Hmmm really ? I thought the tranny box works with GL4 and 5 and the Rear diff is 5 ????" Is not ? ... IS the other way around ? ...... ?????? " ...

phew .... My brain is working .... yes ! .... :)


Im gonna go get some 75w90NS then. :) See if it helps my Tranny whine issue. I have this issue B4 and after my clutch swap so its not the clutch pedal issue. (I will adjust it later the day, however)

Thanks Team :)

Oh great, another expert :icon_no2: The Mazda RX-8 Manual Transmission (Y16M-D) Service Manual calls out 75W90 in either API Service Spec GL4 or GL5.


The original recomendation (2004-6) was for a GL4/GL5 combo fluid for the trans.

After countless trans failures due to syncro wear, the recomendation was changed in 2006 to a GL4-only manual tranmission fluid.


The issue is whether or not the oil has limited slip lube in it, which most standard gear oils do.


Not really - the limited slip additives do wear on syncros and oils with this should not be used, but the main issues are the specific Extreme Pressure (EP) additives (that are required to meet GL5 specs for gear oils) that are very hard on the soft metals used for many syncros. GL4 oils do have some antiwear additives, but not the ones that are so hard on syncros.

This does cause a tradeoff dilema, to get less wear on the syncros, you have to have less EP additives, which creates the potential for more wear on the trans gears themselves - but most of our trans failures are due to syncro failures (or slow working syncros causing poor shifts breaking gear teeth) and not due to actual tooth wear (with the possible exception of the pure racers like Team)


Redline MTL isn't heavy enough. If you push it hard with this lube the trans will eventually have a catastrophic failure. I know, it cost me trans #2.


Possibly - depends on application. I know you race and you need a high viscosity oil with lots of EP additives for the very high temps and extreme loads you see.

But for the average mostly street driven vehicle, MT90 straight will provide very good protection and if you mix 50/50 with MTL, you would still have good protection with much better shifting. I would not do the latter for racing applcations, but for normal street use, it could be a good compromise of protection and good shifting.

Also, here is RL's actual recommendations for transimission via their brochure

"TRANSMISSIONS - MTL® can be used in most manual
transmissions and transaxles for both street and racing
use unless the manufacturer requires the additional protection
of an SAE 90 or the extreme-pressure protection
of a GL-5. In those situations the MT-90 (GL-4) or
75W90NS (GL-5) will provide good shiftability and synchro
compatibility and extra gear protection.
LightWeight Gear Oil can be used in transmissions calling
for a 75W or 80W GL-5. 75W140NS will provide
greater high-temperature viscosity, reducing gear noise
and rattle. D4 ATF can be used where the manufacturer
calls for an ATF as the D4 has GL-4 gear protection
and provides the best low-temperature shiftability."


While some tranmissions are designed to handle non limited-slip GL-5 gear oils, our trans has been having issues with it due to our syncro's soft metals, causing issues over time and thus the changing of the recomendation - your choice, but I do use a GL-4 only and would recommend avoiding any GL5 or combo GL4/GL5 gear oils in your manual trans.

The original recomendation (2004-6) was for a GL4/GL5 combo fluid for the trans.

After countless trans failures due to syncro wear, the recomendation was changed in 2006 to a GL4-only manual tranmission fluid.



Not really - the limited slip additives do wear on syncros and oils with this should not be used, but the main issues are the specific Extreme Pressure (EP) additives (that are required to meet GL5 specs for gear oils) that are very hard on the soft metals used for many syncros. GL4 oils do have some antiwear additives, but not the ones that are so hard on syncros.

This does cause a tradeoff dilema, to get less wear on the syncros, you have to have less EP additives, which creates the potential for more wear on the trans gears themselves - but most of our trans failures are due to syncro failures (or slow working syncros causing poor shifts breaking gear teeth) and not due to actual tooth wear (with the possible exception of the pure racers like Team)



Possibly - depends on application. I know you race and you need a high viscosity oil with lots of EP additives for the very high temps and extreme loads you see.

But for the average mostly street driven vehicle, MT90 straight will provide very good protection and if you mix 50/50 with MTL, you would still have good protection with much better shifting. I would not do the latter for racing applcations, but for normal street use, it could be a good compromise of protection and good shifting.

Also, here is RL's actual recommendations for transimission via their brochure

"TRANSMISSIONS - MTL® can be used in most manual
transmissions and transaxles for both street and racing
use unless the manufacturer requires the additional protection
of an SAE 90 or the extreme-pressure protection
of a GL-5. In those situations the MT-90 (GL-4) or
75W90NS (GL-5) will provide good shiftability and synchro
compatibility and extra gear protection.
LightWeight Gear Oil can be used in transmissions calling
for a 75W or 80W GL-5. 75W140NS will provide
greater high-temperature viscosity, reducing gear noise
and rattle. D4 ATF can be used where the manufacturer
calls for an ATF as the D4 has GL-4 gear protection
and provides the best low-temperature shiftability."


While some tranmissions are designed to handle non limited-slip GL-5 gear oils, our trans has been having issues with it due to our syncro's soft metals, causing issues over time and thus the changing of the recomendation - your choice, but I do use a GL-4 only and would recommend avoiding any GL5 or combo GL4/GL5 gear oils in your manual trans.

Im researching the issue atm, and I ran outside b4 just to get myself a few bottles of MT-90 (Damn its fuxking expensive to buy them locally, 13.99 per quart + tax ! Argh !)

Now Im wondering, is my syncro still good or is it about to go. Like I said now whenever I shift @ faster than 30 mph I will get that *BOV kind of whine*.

meh ... How much is a rebuild tranny selling for again ? :)

Im researching the issue atm, and I ran outside b4 just to get myself a few bottles of MT-90 (Damn its fuxking expensive to buy them locally, 13.99 per quart + tax ! Argh !)

Now Im wondering, is my syncro still good or is it about to go. Like I said now whenever I shift @ faster than 30 mph I will get that *BOV kind of whine*.

meh ... How much is a rebuild tranny selling for again ? :)

Could be that you have some syncro wear - it is hard to tell because our syncros whine with the stock fluid (and some others) pretty bad, so it may or may not be from wear.

I think I mentioned before I have had success and almost totally eliminated any whine with the BG Syncroshift II (which is their full synthetic GL-4). It is slightly thinner than the 90 weight that is called for in the manual, so it is great for street use but likely not thick enough for tracking/racing, but has a great additive pack and shifts very, very well. It is a little hard to find, but almost everyone that has tried it swears by it.

RL's MT-90/MTL are also great GL-4 fluids for protection (not as good as the GL-5, but is it worth it), but MT90 is not known for being very good for shift quality unless you mix it 50/50 with MTL. MTL shifts great, but with a thinner gear oil that would likely be fine for normal street use, except for very hot climates.

RP's MaxGear 75W90 combo GL4/5 is a great fluid from a protection standpoint, I would just be concerned on the EP additives (and limited slip additives) causing increased syncro wear over time. For a trans designed to handle it, it is great, but I am not sure our syncros will hold up over the long haul using it. For the diff, it is great to use.

AMSOIL also makes their equivalent to RL's MT-90/MTL (MTG/MTF) that are GL-4 only, also very good, and could be combined 50/50 for a similar shift feel to an RL 50/50 mix.

As persnickiny as our trans is, I am not sure I would go with any lessor brands than these.

Thanks Jax :)

Your input on oil matters, as always, is appreciated

He's my singular resource for automotive fluids and has never steered me wrong.:)

Could be that you have some syncro wear - it is hard to tell because our syncros whine with the stock fluid (and some others) pretty bad, so it may or may not be from wear.

I think I mentioned before I have had success and almost totally eliminated any whine with the BG Syncroshift II (which is their full synthetic GL-4). It is slightly thinner than the 90 weight that is called for in the manual, so it is great for street use but likely not thick enough for tracking/racing, but has a great additive pack and shifts very, very well. It is a little hard to find, but almost everyone that has tried it swears by it.

RL's MT-90/MTL are also great GL-4 fluids for protection (not as good as the GL-5, but is it worth it), but MT90 is not known for being very good for shift quality unless you mix it 50/50 with MTL. MTL shifts great, but with a thinner gear oil that would likely be fine for normal street use, except for very hot climates.

RP's MaxGear 75W90 combo GL4/5 is a great fluid from a protection standpoint, I would just be concerned on the EP additives (and limited slip additives) causing increased syncro wear over time. For a trans designed to handle it, it is great, but I am not sure our syncros will hold up over the long haul using it. For the diff, it is great to use.

AMSOIL also makes their equivalent to RL's MT-90/MTL (MTG/MTF) that are GL-4 only, also very good, and could be combined 50/50 for a similar shift feel to an RL 50/50 mix.

As persnickiny as our trans is, I am not sure I would go with any lessor brands than these.

The whine is getting *worst* over these 2-3 K miles. So not sure if its really that bad or Syncro is about to *go*.

but I mean our tranny is known to be one of the weakspot, so Im not surprise if it dies.

Im gonna try to pour some MT-90 into the tranny either today or wednesday and see what happens. If the shift quality is bad (or grinds ..) then Im gonna mix it with MTL or try BG.

Even if my tranny dies, I can still go back and tell those dealership suckers to fix it, since I still have my receipts for Tranny fluid, and I change my fluid like almost every 15K miles.

Thx for ur words :)

Thanks Jax :)
Your input on oil matters, as always, is appreciated


He's my singular resource for automotive fluids and has never steered me wrong.:)


Thx for ur words :)


Thanks for the kind words - happy to share what I can.

I always though the BG Synchroshift II was a 75W90...

I always though the BG Synchroshift II was a 75W90...

No - it is a 70W80, a little thinner - about like mixing RL MT90 and MTL in a 50/50 mix.

I hate to engage in "toldja so" proclamations but I have been telling you guys for quite a while now that the factory-spec oil in the driveline is the best choice for street driving. There was a point a long while back where MM and I discussed in a thread the potential that the clinging/thicker oils weren't flowing as Aisin had intended and that they were causing the synchros to not slide or spin-up as freely. I have tried all different kinds of tranny fluids and the $8/qt. Mobil1 has always worked great for me.

I think I mentioned before I have had success and almost totally eliminated any whine with the BG Syncroshift II (which is their full synthetic GL-4). It is slightly thinner than the 90 weight that is called for in the manual, so it is great for street use but likely not thick enough for tracking/racing, but has a great additive pack and shifts very, very well. It is a little hard to find, but almost everyone that has tried it swears by it.


I ran a mix of this and Red Line heavy duty shock proof in my all wheel drive eagle talon. This combo worked great on that car. The 170,000 mile original transmission shifted beautifully and held up to repeated 500 hp drag launches with no issues.

I've had my RX-8 almost two weeks now, it shifts great. But I have no idea if the original owner ever changed the tranny or diff fluids so I've been planning on doing this in the near future. Would this be a good setup for my RX-8? Or is there a better option since mine doesn't exhibit any shifting problems?


It is a little hard to find, but almost everyone that has tried it swears by it.

Heres were I bought it for my talon. http://www.slowboyracing.com/estore/home.php?cat=5304


I've also got a '93 Miata I use for STS2 autoX. I put Royal Purple in it and it works great in the spring, summer, and fall months. But in the cold winter months the tranny grinds the first couple of shifts, so I think I'll stay away from it for my RX-8.

has anyone ever been denied a new transmission from mazda?
because i was told that "This is the last transmission were giving you"
im on my third one, first one went out when i first got the car, second one went out due to the syncros..?

and i found that the 5w20 oil burns up much much quicker than the 5w30.

has anyone ever been denied a new transmission from mazda?
because i was told that "This is the last transmission were giving you"
im on my third one, first one went out when i first got the car, second one went out due to the syncros..?

and i found that the 5w20 oil burns up much much quicker than the 5w30.

Tons, depends on what ur dealership do.

I ran a mix of this and Red Line heavy duty shock proof in my all wheel drive eagle talon. This combo worked great on that car. The 170,000 mile original transmission shifted beautifully and held up to repeated 500 hp drag launches with no issues.

I've had my RX-8 almost two weeks now, it shifts great. But I have no idea if the original owner ever changed the tranny or diff fluids so I've been planning on doing this in the near future. Would this be a good setup for my RX-8? Or is there a better option since mine doesn't exhibit any shifting problems?

Heres were I bought it for my talon. http://www.slowboyracing.com/estore/home.php?cat=5304

I've also got a '93 Miata I use for STS2 autoX. I put Royal Purple in it and it works great in the spring, summer, and fall months. But in the cold winter months the tranny grinds the first couple of shifts, so I think I'll stay away from it for my RX-8.

Interesting mix, but I would still shy away from the RL Shock Proof in the trans as it is a GL-5 oil - try the straight BG Syncroshift II and see what you think or use a combo the BG and RL MT-90 as it is a GL-4 only oil if you want to tray something similar to what you used before.

Thanks for the link - this is a good place to buy BG trans/gear oils that I have seen many people use - good descriptions of oils as well on site.

The Miata uses a very similar (almost the same) trans as the 8 - you are experiencing what many others have highlighted using RP MaxGear in the RX8 trans - like I said above, I would shy away from this for the trans of an 8 or a Miata (great for the diff though)

As far as engine oil I use Havoline 5W-30 or 20 in the winter. I'm about to start mixing in a qt/liter of Motul 300V 5W-40 every oil change and probably as the filler in between changes since it is safe to mix with non-sythetics. Crazy expensive but I think the best solution if you don't want to take the full-on synthetic plunge.

http://www.p1-performance.com/pdf/300VPower5W-40_3601.pdf

Already have 2L of the MotylGear 75W-90 for the trans just haven't put it in. The removal of GL5 specs has me hesitant as it's a GL4 & 5. Safe for all yellow metals though so I will put it in.

I hate to engage in "toldja so" proclamations but I have been telling you guys for quite a while now that the factory-spec oil in the driveline is the best choice for street driving. There was a point a long while back where MM and I discussed in a thread the potential that the clinging/thicker oils weren't flowing as Aisin had intended and that they were causing the synchros to not slide or spin-up as freely. I have tried all different kinds of tranny fluids and the $8/qt. Mobil1 has always worked great for me.

I'd have to agree with this here. My tranny felt best when it was still on the stock oil. The question is, where can we get our hands on the stock oil that came with the tranny?

I just use 75-90 Mobil1 as a factory-like replacement.

I just use 75-90 Mobil1 as a factory-like replacement.

But remember Charles, M1 Gear oil is a GL-5 oil (I don't even think is is a combo GL-4/GL-5) and most others over the counter are the same - I would still stick with a GL-4 only fluid.

The dealer did my first tranny fluid change for me, and it felt far smoother than the factory one. They didn't tell me what it was, except it was "synthetic". This mystery oil is still in my tranny..., and I don't get any of the whining or problems some of you seem to be facing.

Anyway, thus far, I have decided the following for my engine:
-Castrol GTX 5W30 for the engine.
-Redline 75W30 for the diff

No idea what I should pick for the tranny still..., Jax? I just want one that is the best damned thing money can buy.

it you granny shift that 50/50 recommendation is fine, push it hard and you will pay the price ...

But remember Charles, M1 Gear oil is a GL-5 oil (I don't even think is is a combo GL-4/GL-5) and most others over the counter are the same - I would still stick with a GL-4 only fluid.

Not to mention Mobil1 calls it a gear oil since it contains limited slip additives. When I called them they said they don't make a manual trans fluid. Of course SpeedSource uses Mobil1 in their trans but I don't know what. In other countries you can buy Mobil1 manual trans fluid - Mobilube SHC 75W-90
http://www.ibg.ge/lubricant.asp?lubID=14

The dealer did my first tranny fluid change for me, and it felt far smoother than the factory one. They didn't tell me what it was, except it was "synthetic". This mystery oil is still in my tranny..., and I don't get any of the whining or problems some of you seem to be facing.

Anyway, thus far, I have decided the following for my engine:
-Castrol GTX 5W30 for the engine.
-Redline 75W30 for the diff

No idea what I should pick for the tranny still..., Jax? I just want one that is the best damned thing money can buy.

75w30 ? .................................... :lol:

it you granny shift that 50/50 recommendation is fine, push it hard and you will pay the price ...

I got 3 bottles of MT-90 the other day. cuz I dont really like the idea of mixing it with MTL. I searched and found a lot of post saying that people with *pure MT-90* have some really poor shifting quality issue, Im just wondering how *poor* it can be? is it like grinding(I hate it) or just not very smooth ????

it you granny shift that 50/50 recommendation is fine, push it hard and you will pay the price ...

As you can see from my sig pic, I race this car. I don't granny shift.

As you can see from my sig pic, I race this car. I don't granny shift.

then maybe u should get 75w140ns

I'm lazy to correct my typo.

But remember Charles, M1 Gear oil is a GL-5 oil (I don't even think is is a combo GL-4/GL-5) and most others over the counter are the same - I would still stick with a GL-4 only fluid.

J, this got me thinking so I looked in the FSM for specified lubes and such. Have I missed or otherwise forgotten the latest info about what is working for us? In the FSM, Mazda lists GL-4 or GL-5 in 75W-90 as an all-season lube for the tranny and GL-5 in SAE 90 for the diff. That's why I use the Mobil1 when I am not experimenting with other lubes.

J, this got me thinking so I looked in the FSM for specified lubes and such. Have I missed or otherwise forgotten the latest info about what is working for us? In the FSM, Mazda lists GL-4 or GL-5 in 75W-90 as an all-season lube for the tranny and GL-5 in SAE 90 for the diff. That's why I use the Mobil1 when I am not experimenting with other lubes.

No TSB/MSB that I am aware of - it seems Mazda just quietly changed the recommendation in the owners manuals - probably to not have to pay warranty claims on trans that fail (syncros) due to the use of a GL-5 lubricant.

Okay. Thank you, Sir.:) Was that back when Mazda was intructing the dealer techs to mix the fluids?

Okay. Thank you, Sir.:) Was that back when Mazda was intructing the dealer techs to mix the fluids?

Not sure what you are referring too on that one.

Best I can remember, the changeover in the recomendation came in 2006 to a GL-4 oil for the trans.

Sir, as in a moniker denoting respect. Oh, you mean my other comment....:lol2:

A couple years ago Mazda told their dealer techs to blend a bit of ATF in with the M/T fluid. I don't recall what the ratios were nor why they were doing it. Probably synchro grinding.

I hate reading this site. Always making me 2nd guess anything I've done.

I put this Amsoil gear oil in both my tranny and diff.

http://www.amsoil.com/storefront/svg.aspx

When the weather was really cold (-20C / 0F) I'd get some minor grind if I tried to shift fast until the car really warmed up. Now that the weather is warmer (approx 0C/32F), it seems fine no matter how fast I shift.
Does that oil look ok? And has anyone else seen cold weather shift issues regardless of oil used?

The car is an 04, Oil went in at 46k km [29k mi], just a few months after I bought it.

I would bet a paycheck(if I still got them) that your shifting troubles are from that particular lube to be of the "clinging types" that I warn people about. Severe Duty oils, and others like them, often have the tendency to try and absorb the driveline shock by clinging to the synchros and gears as they turn. The problem with this, and this is strictly my own opinion, comes by way of the clinging nature also causing the synchros to fail to spin up or down quickly enough to meet the speed of the shaft they are attempting to mesh with.

I would bet a paycheck(if I still got them) that your shifting troubles are from that particular lube to be of the "clinging types" that I warn people about. Severe Duty oils, and others like them, often have the tendency to try and absorb the driveline shock by clinging to the synchros and gears as they turn. The problem with this, and this is strictly my own opinion, comes by way of the clinging nature also causing the synchros to fail to spin up or down quickly enough to meet the speed of the shaft they are attempting to mesh with.

So the theory is that certain oils will over lubricate the synchros? Reducing the friction to the point where they can't spin the shafts quickly enough for fast shifting? If I have no problems with it in the warmer months, and can live with shifting slowly during cold weather warm ups, I'm guessing I should be fine leaving this oil in?

Not exactly.

Not exactly.

The theory on why there is grinding, or the theory that I'd be ok to leave the oil in :)

I hate reading this site. Always making me 2nd guess anything I've done.

I put this Amsoil gear oil in both my tranny and diff.

http://www.amsoil.com/storefront/svg.aspx

When the weather was really cold (-20C / 0F) I'd get some minor grind if I tried to shift fast until the car really warmed up. Now that the weather is warmer (approx 0C/32F), it seems fine no matter how fast I shift.
Does that oil look ok? And has anyone else seen cold weather shift issues regardless of oil used?

The car is an 04, Oil went in at 46k km [29k mi], just a few months after I bought it.

AMSOIL Severe Gear is a GL-5 lubricant that is great for your rear diff - and will absolutely, over time kill the syncros in your trans.

For your trans, you want AMSOIL MTG (Assuming you want to use AMSOIL products)

http://www.amsoil.com/StoreFront/mtg.aspx

or for better shifting, you can mix 50/50 with AMSOIL MTL

http://www.amsoil.com/StoreFront/mtf.aspx

As for your other question on trans fluids, Charles is right in that GL-5 fluids do not have the right "grabbiness" (a technical term) for syncros to work efficiently - they do tend to be too slick as they have many Friction Modifiers (FMs) in addition to the EP additives.

But the real issue with GL-5 fluids in a trans with syncros is that syncros use softer metals and GL-5 fluids have way too much Extreme Pressure (EP) additives that actually wear out these softer metals over time, reducing the ability of your syncros to function properly until they just eventually fail.

GL-4 fluids, like the ones I linked above, have some EP adds, but tend to be formulated for the "right" friction for the syncros to work properly and also have much less EP additives (usually different ones as well) to keep from prematurely wearing out the syncro soft metals.

Also, there are many GL4/GL5 combo fluids, like RPs Max Gear, BG Ultraguard, etc, etc, that claim to work in manual trans and diffs. Some use and seem to have successwith these fluids in manual transmissions, but I would shy away from these combo fluids in a manual trans as they will still have too many EP and FM additives (which are required to meet the GL5 spec) for good syncro operation and wear - not all agree with this, but I would rather be safe than sorry as trans rebuilds are not cheap as most of our trans failures seem to be from the syncros failing (or being so slow in operation that we grind the trans gear teeth or break them off completely).

Have you ever seen, not heard, but seen anyone blowing their engine because of the oil they picked?
I'm sure $1.49 warren oil from Winn Dixie would do just as well, It's all a bunch of crap just change it regularly and relax. $6 a quart won't make any difference you maniacs.

Have you ever seen, not heard, but seen anyone blowing their engine because of the oil they picked?
I'm sure $1.49 warren oil from Winn Dixie would do just as well, It's all a bunch of crap just change it regularly and relax. $6 a quart won't make any difference you maniacs.

thanks for clearing that up for us..

how did we miss this....

beers :beer:

Have you ever seen, not heard, but seen anyone blowing their engine because of the oil they picked?
I'm sure $1.49 warren oil from Winn Dixie would do just as well, It's all a bunch of crap just change it regularly and relax. $6 a quart won't make any difference you maniacs.

Have fun

Have you ever seen, not heard, but seen anyone blowing their engine because of the oil they picked?
I'm sure $1.49 warren oil from Winn Dixie would do just as well, It's all a bunch of crap just change it regularly and relax. $6 a quart won't make any difference you maniacs.


We're talking about transmission and differential fluids right now, idiot.

We're talking about transmission and differential fluids right now, idiot.

Forgive him, Ray.

There are people on earth who still cannot read.

I told him to have fun already.

Just forgive him :)

We're talking about transmission and differential fluids right now, idiot.

LoL Finally someone got ray mad :) :lol: :lol:

The only person who truly annoyed me on this forum was Tajabaho with his incessant tweaking of his nitrous system. On the other hand, he did prove for me that I am so good at it that even he couldn't screw it up.:lol2: When I use the terms "asshole" and "idiot" they are usually in a big-brotherly, Denis Leary, sorta way.

Good old Leary..... I met him in real life once!

Have you ever seen, not heard, but seen anyone blowing their engine because of the oil they picked?
I'm sure $1.49 warren oil from Winn Dixie would do just as well, It's all a bunch of crap just change it regularly and relax. $6 a quart won't make any difference you maniacs.

Hey dude, when you're ready to upgrade your exhaust, you can save tons of money using this device instead of one of those thousand dollar setups.


http://cgi.ebay.com/ebaymotors/Exhaust-Tip-Muffler-Insert-rx8-rx-8-6-6s-3-3s-Miata_W0QQcmdZViewItemQQcategoryZ33633QQihZ014QQit emZ330225502544QQrdZ1QQsspagenameZWDVW

http://www.rx8club.com/showthread.php?t=142424

Next time I change my transmission oil, I'm thinking about perhaps going to a mineral oil formulation as we don't seem to have a ton of luck with the synthetics. Does anyone have any experience using the conventional mineral oil gear lubes?

Also, what about Synchromesh oils? We seem to be having issues with the synchros spinning up to speed and Synchromesh would seem to be just the ticket to solve that. Perhaps a half or full quart cocktail mixed into our gear oil would be a solution?

We're talking about transmission and differential fluids right now, idiot.

You are, not me, Mental midget!

You win. I have engines to build and product to develop.

Next time I change my transmission oil, I'm thinking about perhaps going to a mineral oil formulation as we don't seem to have a ton of luck with the synthetics. Does anyone have any experience using the conventional mineral oil gear lubes?

Also, what about Synchromesh oils? We seem to be having issues with the synchros spinning up to speed and Synchromesh would seem to be just the ticket to solve that. Perhaps a half or full quart cocktail mixed into our gear oil would be a solution?

You can just go for MT-90 I think. I have it, but havent had a chance to put it into my tranny yet. It should be good for Synchros, but ppl said the shifting quality suck.

I used MT-90 as my first oil change and the shift quality went right out the window - slow like mollasses in January.

Mixed about 1/3rd 'MTL' with the 90 weight for a silky smooth shift.

I hear the RP and Syncro stuff is a little thinner, right out of the bottle......


S

I have RP, Shifting has been silk ...

So maybe I should mix it down with a bit of MT-90 ?

My favorite oil, now don't beat me up over this, take it in the spirit in which it was meant. My favorite oil is, are you ready for this ??????? Here goes...................................Extra Virgin Olive Oil. ( pun intended )

Mazola FTW !

You can just go for MT-90 I think. I have it, but havent had a chance to put it into my tranny yet. It should be good for Synchros, but ppl said the shifting quality suck.

I have MT-90 and do not like it. I also have tried RP MaxGear and while I liked it a bit more, it's still far from OEM. You should know this by now...

I have MT-90 and do not like it. I also have tried RP MaxGear and while I liked it a bit more, it's still far from OEM. You should know this by now...

RP Max Gear 75w90 is a GL5. It worked great for a while. However after a while each time I changed transmission fluids the issues with 3-4 upshift grinding at high rpms got gradually worse till my transmission was replaced by Mazda. By that time, it would grind anywhere around 4.8k rpm. When the issues first started, it was intermittent at close to 7k rpms.

I have no plans to ever use maxgear in my transmission again. Maxgear is still in my diff however.

RP Max Gear 75w90 is a GL5. It worked great for a while. However after a while each time I changed transmission fluids the issues with 3-4 upshift grinding at high rpms got gradually worse till my transmission was replaced by Mazda. By that time, it would grind anywhere around 4.8k rpm. When the issues first started, it was intermittent at close to 7k rpms.

I have no plans to ever use maxgear in my transmission again. Maxgear is still in my diff however.

At this point I don't want to use either MaxGear or MT-90 when I do my next tranny oil change.

I used MT-90 as my first oil change and the shift quality went right out the window - slow like mollasses in January.



Yeah, when I did my first change at around 50k miles, using MT-90 really didn't improve things over the old oem fluid. Going to probably go a 50/50 mix of MT-90/MTL next time.

If i take my 8 to the track about 7~9 days a year (probably every other month or so), and wanting to stick with amsoil, what do you recommend, jax_rx8?
according to teamrx8's previous post in this thread, using a 50/50 mix doesn't seem like a good idea if i'm pushing the car at the track. I'm not racing like he is, but i know track days can be hard on the car.

i'm guessing, amsoil svg(gl-5) for the rear diff. and mtg(gl-4) for the trans?


AMSOIL Severe Gear is a GL-5 lubricant that is great for your rear diff - and will absolutely, over time kill the syncros in your trans.

For your trans, you want AMSOIL MTG (Assuming you want to use AMSOIL products)

http://www.amsoil.com/StoreFront/mtg.aspx

or for better shifting, you can mix 50/50 with AMSOIL MTL

http://www.amsoil.com/StoreFront/mtf.aspx

As for your other question on trans fluids, Charles is right in that GL-5 fluids do not have the right "grabbiness" (a technical term) for syncros to work efficiently - they do tend to be too slick as they have many Friction Modifiers (FMs) in addition to the EP additives.

But the real issue with GL-5 fluids in a trans with syncros is that syncros use softer metals and GL-5 fluids have way too much Extreme Pressure (EP) additives that actually wear out these softer metals over time, reducing the ability of your syncros to function properly until they just eventually fail.

GL-4 fluids, like the ones I linked above, have some EP adds, but tend to be formulated for the "right" friction for the syncros to work properly and also have much less EP additives (usually different ones as well) to keep from prematurely wearing out the syncro soft metals.

Also, there are many GL4/GL5 combo fluids, like RPs Max Gear, BG Ultraguard, etc, etc, that claim to work in manual trans and diffs. Some use and seem to have successwith these fluids in manual transmissions, but I would shy away from these combo fluids in a manual trans as they will still have too many EP and FM additives (which are required to meet the GL5 spec) for good syncro operation and wear - not all agree with this, but I would rather be safe than sorry as trans rebuilds are not cheap as most of our trans failures seem to be from the syncros failing (or being so slow in operation that we grind the trans gear teeth or break them off completely).

If i take my 8 to the track about 7~9 days a year (probably every other month or so), and wanting to stick with amsoil, what do you recommend, jax_rx8?
according to teamrx8's previous post in this thread, using a 50/50 mix doesn't seem like a good idea if i'm pushing the car at the track. I'm not racing like he is, but i know track days can be hard on the car.

i'm guessing, amsoil svg(gl-5) for the rear diff. and mtg(gl-4) for the trans?

I agree with Team if you are tracking or Auto-Crossing - your choices are right on IMHO.

You could even consider AMSOILs Severe Gear 75W110 for the diff as well for that little extra protection (I assume you were referring to the 75W90), with your tracking and especially if you are in a warmer climate zone

RP Max Gear 75w90 is a GL5. It worked great for a while. However after a while each time I changed transmission fluids the issues with 3-4 upshift grinding at high rpms got gradually worse till my transmission was replaced by Mazda. By that time, it would grind anywhere around 4.8k rpm. When the issues first started, it was intermittent at close to 7k rpms.

I have no plans to ever use maxgear in my transmission again. Maxgear is still in my diff however.

For some reason, the Tranny whine that I got 2 weeks ago is now *gone*

Have been using RP Maxgear in my tranny since 5K miles

hmm ... but still I think I will try MT-90 b4 I go try Amsoil or anything else :)

For some reason, the Tranny whine that I got 2 weeks ago is now *gone*

Have been using RP Maxgear in my tranny since 5K miles

hmm ... but still I think I will try MT-90 b4 I go try Amsoil or anything else :)


no doubt the maxgear feels better / smoother than the stock oils. If you search my old posts under mysql101, you'll see I recommended maxgear for many years too.

The issues started up after ~20,000 miles with maxgear in the transmission. And it wasn't a constant thing, the grinding happened once in a while. Infrequent enough that I thought I wasn't clutching far enough. It's also interesting that with each oil change (I changed tranny fluids once a year) it seemed to get worse. Perhaps results would be different if I only changed the oil once every 50k miles.

My personal recommendation is to switch to something else ASAP.

no doubt the maxgear feels better / smoother than the stock oils. If you search my old posts under mysql101, you'll see I recommended maxgear for many years too.

The issues started up after ~20,000 miles with maxgear in the transmission. And it wasn't a constant thing, the grinding happened once in a while. Infrequent enough that I thought I wasn't clutching far enough. It's also interesting that with each oil change (I changed tranny fluids once a year) it seemed to get worse. Perhaps results would be different if I only changed the oil once every 50k miles.

My personal recommendation is to switch to something else ASAP.

I agree.

This is the problem with GL5 or combo GL4/5 gear oil use - everything can seem fine for quite a long time as the additional wear to the syncros happen slowly, but surely.

By the time the symptoms start showing from the additional wear, it is too late and the damage is done. Then you are left with nursing the trans as far as you can until your eventual rebuild.

I finally decided to drop the cash for Redline MT-90 for the trans, and Redline 75w90 Gear Oil for the diff.

no doubt the maxgear feels better / smoother than the stock oils. If you search my old posts under mysql101, you'll see I recommended maxgear for many years too.

The issues started up after ~20,000 miles with maxgear in the transmission. And it wasn't a constant thing, the grinding happened once in a while. Infrequent enough that I thought I wasn't clutching far enough. It's also interesting that with each oil change (I changed tranny fluids once a year) it seemed to get worse. Perhaps results would be different if I only changed the oil once every 50k miles.

My personal recommendation is to switch to something else ASAP.

I did read your thread (come on, u think I made 6817 post/being a member since Jun 2005 for nothing? :))

I agree.

This is the problem with GL5 or combo GL4/5 gear oil use - everything can seem fine for quite a long time as the additional wear to the syncros happen slowly, but surely.

By the time the symptoms start showing from the additional wear, it is too late and the damage is done. Then you are left with nursing the trans as far as you can until your eventual rebuild.

I have RP in my gear for over 35K miles already. Still alive but ... "its better be safe than sorry" ... I should change it out.

Ok, Im gonna change The tranny fluid out this wednesday to Pure MT-90. (I have to change my winter tires out + Autoexe Under brace in anyway :))

Lets see how shitty the shifting will be lol :)

The NB 6-speed guys seem to like the Motorcraft Full Synthetic Manual Transmission Fluid quite a lot. Since that tranny is a close cousin of ours, I'm wondering if it'll work well for us as well. It's very expensive though, but if it's a good cure it might be work it. Jax?

Thread here: http://forum.miata.net/vb/showthread.php?t=270393

I have MT-90. No problem.

Shift Quality ? I think it feels about the same if not better. it feels *tight* hahaa

I'm using Redline Heavy Shockproof for the tranny. It has film thickness similar to a 75W250 grade, while providing the same low fluid friction as an SAE 75W90. Also, it looks like a strawberry smoothie. A couple of other members here uses the same thing and it feels great. :)

This blows. After a while of silky smooth shifting with MT-90, it's starting to feel rather knobby and hard to shift.

Fuck this. I'll need to swap into something else as soon as I get back from my summer vacation.

I've read all the recommendations till now..., and quite frankly, it's left me more confused than before. Everyone has their own "trick" and "secret".

So do tell me if you think my new choice is gonna cause problems.

I'm going to try Redline MT-90 again, except this time I mix it 1/3 with MTL.

^ won't be a problem.. I'm using about a 60/40 ratio MT-90 / MTL.. shifting is great.

Also, the first tranny change with a certain fluid is basically a rinse cycle- on the 2nd one you'll see most of the benefits

I have MT-90 for couple of months and it shifts just fine.

I came from Royal Purple's Maxgear.

http://www.amsoil.com/storefront/svt.aspx

http://www.amsoil.com/storefront/mtg.aspx

Low temp 1-2 notchiness is gone. Smoother shifting to all gears and everything is whisper quiet, no low speed whine. Nothing.

i gota get rp out of my tranny

ive had it for about 3 weeks now

Use RedLine for your Tranny.

Yeah its being shipped as i speak
Full mt-90

Havoline for the dino juice. Best moly levels and additive package of all.

Yeah its being shipped as i speak
Full mt-90

Enjoy your notchy shifting.

thanks for the info. very good stuff

Enjoy your notchy shifting.

Mine shifts just fine like RP. and RP was smoother than Stock.

oh yes, pure MT-90 here. :)

After a few hours of reading, I'm leaning toward Severe Gear 75W-110 for my diff, possibly with Slip Lock friction modifier added. For the transmission, I think I'm going with MTG. I'm considering going 25% MTF to protect the synchros - I'm mainly daily driver on this car, but I'm going to start HPDEs, maybe twice a year. I live in Phoenix.