RX-8 manual transmission oil preferences?
 

Hey team.

There is alot of posts about Rx-8 manual transmission and the oil shops / home mechanics use. Most common I hear being used is Redline MT-90. Why is this one the preferred oil or has it just become a cult classic and go to for most people to suggest and use?

Isn't any GL 4 75-80W transmission oil suited for this?

Also is there any info on why synthetic or mineral oil would be better for these transmissions?

Any info and insight is welcome!

I've tried a few brands, but redline MT-90 has been a world of difference. I cannot recommend anything else. I tried Royal purple's and my trans was grinding every shift. Swapped back to MT-90 and it smoothed out.

I tried this Ford Motorcraft XT-M5-QS for a while and found it resulted in notchy shifting except in the middle of summer. The RedLine is working well for me (-10° to 40° Celsius).

Anything will be better than your old gear oil.

I use Eneos

Redline MT-LV
 

I use MT-LV, and so does Meat Head, last I checked. Not MT-90. I have tried many, including MT-90, and MT-LV is the best. There is a thread about it on the forum.

Cocktail of MT90 and MTL. I may try MT-LV next time.

Another vote for Redline MT-90 from myself.

MT-90 user here!

Sonny

Just posted this in my build thread, so will cross-post here:

Where are you located and under what temperature range does your 8 operate? I’m due to change transmission and differential oil soon.

I'm in the Bay Area these days. Lived in the PNW before that. I've driven it in the snow a few times in the past, but will probably never need to do that again. I autocross at Crow's Landing sometimes, which is usually sweltering. So, between 40°-105°F, generally.

Thanks - I’m a couple hours north of Seattle with similar conditions. Just wanted to confirm if I switch gear oil that I’m not having to do “patient” shifts with oil too thick for synchros. Think I’ll try out your suggestion.

You might read through what I posted in the other thread, if you haven't already. Mazda gearboxes don't tolerate much abuse. (I can testify, having had to remove the transmission from my R3 twice in 50k miles.) Hartzel offered some mitigations, but their recommendation is "patient shifts" even in ideal scenarios.

I tend to doubt what this shop says. I have used MTL in a bunch of yellow-metal containing BMW trans for 25 years, and a couple hundred K of street miles and never had a syncro/bushing issue. Corrosion issues, if present, would show up in a street trans with a long drain interval for sure, more than a race trans, I would think. MTL has been around a long, long time.

The man. compatibility quotes Redline states are all for yellow metal suitability. Redline is not perfect, some of their stuff is so-so, but MTL is not suspect at all in my view.

I can see how MTL might not be robust enough under race conditions to keep wear and failure at bay, but corrosion I doubt is a problem.

More info needed.

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+1
RedLine was widely recommended here for years without corresponding failure reports. I've run (still run?) RedLine of one flavour or another for 12 years with no issues.

Losing synchros to fluid corrosion is totally a thing with GL5 fluids in this car, just not with RedLine MT90/MTL.

Always trying to stay current on good/bad/ugly with this car. Appreciate your experience Loki and Kevink0000 along with the new from John. I’m on vacation next week and will collect a sample of what drains out of my S2 transmission since that’s part of my scheduled fun.

IIRC, GL-4 rated gear oil would be appropriate for the Aisin 6speed. MTL and MT90 from Redline are the mainstays not just for RX8 but also Miatas too. There are alternatives if you wish to try.

MTL and MT90 from Redline are the mainstays.......

My 8 is around twenty years old this month and it's on it's fourth fill of redline.

I tried a few fluids when I changed the oil in 'year 2'.
The MT 90 was a bit 'draggy', especially at minus 20 or below.
I finally settled on a 50/50 mix of MT90 and MTL....poifect!

you really need to search and read the many threads on here for this topic, as the opinions vary greatly and honestly seem to be situation dependent

as I found MT90 notchy when cold, but never had any issue at with the Ford Motorcraft oil

another favorable manual transmission oil to consider is Motul 300 75W90 #105777, but you have to be careful as they also offer a 300 “LS” 75W90 oil that’s intended for the differential. The LS stands for limited slip additive it has.

and honestly, given the current times I’m reluctant to use any tranny oil that’s pronounced “anus” (Eneos) :suspect: but that might be your thing.
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what an immature and homophobic thing to bring up on a discussion of transmission oil

It's immature to be sure. But there is no such thing as homophobia. Its a leftist political/legal construct. No need for it to be mentioned here, either.

Aw. The thought police is here. Break it up everyone. No more TRANS oil for you.

no, it was just a play on words, which is quite common by me

it’s equally immature to call me homphobic and all that other worldly triggered garbage, especially by one member who claims to be my brother.

Because I don’t have any phobia; i.e irrational fear, at all regarding the subject. I’m likely as or more familiar with it than the accusers. No, it’s just slurring me with mistruths by the usual suspects.

my familiarity with the that particular culture goes all the way back to the early 1980’s to Orlando, FL when I met my first truly out of the closet friends then, and of all places they worked at Disney World and had quite the internal community there that I met many from back in the day. You guys probably weren’t even born then, or just babies still, and apparently might still be struggling with that some.

You could just as easily ignore me rather than give rise to it, but your action exposes the true intent beyond words. You despise me most of all for that. It’s a different generation now. Back then we would laugh together over it, and just the equal opposite that they would say to me. Today it’s feigned rage and a self righteous cancellation mentality. Compared to your own words towards me, mine are quite innocuous.

but if the mods feel it should be deleted they can tell me and I’ll gladly comply, or they can be inclined to so on their own without any objection from me. I myself have no complaint to them about your own words towards me. Even though your own words and intent rise well above anything in my comment.
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I've been running Amsoil Manual Transmission & Transaxle Gear Lube 75W-90 (https://www.amsoil.com/p/manual-tran...?code=MTGPK-EA) in my RX8 and it seems to be doing well for street duty; shifts are nice and smooth. I've never been on a track with this car so I cannot say how well it does in that situation.

I doubt anyone's "targeting" you sir. I'm certainly not. Heck I don't even know your real name.

You know it's funny, I actually quite liked your post it was well written and informative, that last sentence though.. I found it to be inappropriate and not to gay friendly ( better phrasing Kevin?) Not sure what that has to do with your friends from 40 years ago but I digress.

It's okay though, I think i finally figured you out. You're an extremely intelligent narcissists with a silver keyboard, and I'm sure you'll turn this whole post around on me and cry victim.

But you know what? That okay, I've come to terms with it.
imma go like 200 and suck on my shotgun tonight.

"sonicsdsman" out