Flashwing

I'm always fascinated at the things people splurge on and the things people go cheap on. While I won't say going super cheap on oil is a positive thing, everyone needs to keep in mind that multi-viscosity oils are all a compromise in some fashion.

Some oils provide good efficiency and thus better fuel performance while sacrificing performance protection.

Some oils provide better performance protection but are more inefficient and also don't work well with typical street driving.

Before making well educated decisions about oil viscosity (or choice) you have to understand the benefits and drawbacks of different oil types. You also need to know your oil temperature and pressure. Without temperature and pressure readouts you are making decisions without any basis of what your car is doing.

At the end of the day, these decisions are about bearing protection which doesn't account for the majority of engine failures. Oil continues to be a personal choice often motivated by feelings instead of any hard data. Get some good information, educate yourself on the available choices and choose one that fits the uses of your RX8 with the conditions inside the motor.

GTDave

Most manufacturers specify 5W20 in most of their engines today. Fuel economy (CAFE). It does not mean that 5W20 is the best oil for the application.

It would be interesting to know what the ratio of engine failures have been when comparing the manual transmission models to the automatics. I would bet good money the manuals with the higher redline and more HP fail at a rate that far exceeds the automatic models. I have to wonder what engine speed contributes to failure.

Flashwing

If you're speaking in regards to the RX8, the automatics received quite a large share of engine replacements due to the lower RPM operation and buildup of carbon on seals. The people who tended to "baby" their RX8's the most seemed to be the ones with frequent engine replacements.

pistonhater

Thanks for saying that.

I've been frustrated ever since I came to this site (even before I created an account) with so many people arguing that 5W-20 is bad, causing "early" engine failures, stay away from that oil, etc.

If most engine failures have nothing to do with bearing failure but with internal engine lubrication issues, (seals, carbon buildup,coolant seal failures, loss of compression etc.); why do people keep arguing that oil grade is the damn culprit on these engines?

There's evidence linking abnormal bearing wear with the use of 5W-20 in some engines. In those cases, are we talking about a catastrophic amount of money to replace those "abnormally worn" bearings during a rebuild?

Anyway, thanks for the good info you post on the forums

GeorgeH

iTrader: (2)

I thought that it was (also?) due to the lack of the second oil cooler, resulting in higher oil temps, particularly in hot climates. Or has that been debunked?

PeteInLongBeach

Mazda appears to have gone back and forth on this. I looked at countless automatic RX8s for sale before I bought mine - some had 1 cooler, some had 2. I never thought to notice which year had what. The S2 automatics have 1. I'm guessing the reasoning is that the manual transmission cars will tend to be driven more aggressively.

9krpmrx8

iTrader: (46)

Manual transmission cars have a higher redline and make more power. Oil temps spike in the upper rev range.

9krpmrx8

iTrader: (46)

I agree, running good old Castrol GTX 10W-30 would probably be fine and it is something that is way over thought.

I have had everything tested from Dino Castrol to Mobil 1 and while the results don't translate into much, the Mobil1 has outperformed all the others. My biggest issue before was fuel dilution and the Mobil1 seems to handle that the best and the viscosity stays pretty high even after a full interval. So that is why I am sticking with it. I have had oil pressure and temperature data too look at for a few years now and despite what oil I use, everything seems to stay about the same, even through different motors.

Others use much cheaper oils and they test great. Some (paimon comes to mind) are using stuff like Royal Purple and it is not testing (royal purples own test) so great compared to mine and others Mobil1 0W-40 test results.

It's Voo Doo.

DCIrish

Hey,
I just got my 05 Rx8 shinka. Currently the car has 51K on it, seems to be running fine. I'm looking into changing oil soon but have run into the synthetic vs non problem. I haven't read enough post on this thread to get a "real" answer (because no one really has one) BUT maybe someone savvy will be able to answer this...
lots of people run synth, lots of people don't... so at what mileage have people blown their engines? did they use synth or regular? any trend...?

thanks and hopefully someone has some insight.

bse50

The savvy answer is.. read this whole thread and make your mind up.

PhillipM

And stationary gear failure over here (almost always cars on cheap mineral...)

Harlan

iTrader: (3)

This is pretty informative for those afraid of bearing wear.
http://www.rx7club.com/showthread.php?t=770726
The oil weight may not be that important.

nycgps

iTrader: (1)

can we just use Olive oil and call it a day ?

olddragger

iTrader: (3)

I have had the front bearing wearing on 2 engines. less than 50K on them.
I have always believed the staionary/rotor gears chew up the oil. Its almost like the engine could use a transmission oil with the extreme pressure additives?
I havent gotten a sohn yet---guess I should? Has there been an engine teardown when the sohn adaptor was used only?
I do run redline 5w/30.

Nadrealista

that is one of the reasons why I run mix or regular and race redline oil in mine. they both have very high levels of ZDDP, especially the racing version.

9krpmrx8

iTrader: (46)

I will post up pics soon but this past weekend Shadycrew and HoustonRX8 pulled the engine out of Houston's RX-8 here in San Antonio. Yesterday we spent the day cleaning the parts in preparation to rebuild it and discovered cracks in the housings and the front bearings were worn down to the copper. There was also scorching on the irons, a crushed water seal, and a mysterious sludge in the coolant passages.

This was a re-manufactured engine with 40,000 miles on it, and on time religious oil changes using Castrol GTX 5W-20. My last reman died at 30k of a busted water seal but my bearings looked great so I have come to the conclusion that Mobil1 0W-40 does protect better that the factory recommended 5W-20 in our hot environment.

olddragger

iTrader: (3)

the soarching is prrof pudding the oil got too hot. Did he use water wetter?
Or did someone put alumaseal in the engine?

nycgps

iTrader: (1)

Stock water seal is only good under 230 ish degres, ias far as I remember its a Teflon-rubber-telfon sandwich seal, and the rubber part melts easily. And just like any rubber it cracks over time.

Just rebuild it with some hylomar and it will make the seals last 10 times longer

Cracks in housing? U mean around the spark area? If that's what u are talking about them I gotta tell u its a known issue, u can make it happen less often by adding fins(cuts) at the coolant passage around that area.
And
.. you guys live down south ... just be a man like NYCGPS and use 20w50 already.

don_peppino24

iTrader: (1)

im so lost. i just use castrol 5w-20 and make sure its always topped up. i drive very hard every day (especially on the track) and now at 60,000km its still running fine on original engine.
had a compression test done last year at mazda dealer and everything was good.

i warm the car for 10 min before driving soft for another 10 min until i beat the absolute **** out of it.

if/when the engine fails i'll just rebuild and use it as an excuse to streetport it, maybe get racing beats rotors and ceramic seals or w.e. wow im off topic now.

but yeah i work beside a race shop and they work with rx-8 all the time and use motul synthetic for racing and say they believe its the best oil they've use for rotaries

olddragger

iTrader: (3)

saw the pictures.
I would say he has lubrication problems and maybe some localized overheating problems. His housings really didnt look bad for blowby etc?
How dirty where the rotors?
Maybe his rotor tips where striking the irons a little and thats the reason for those iron wear marks?
Know more when it is speced out. i am really interested in what specs the gears show.

9krpmrx8

iTrader: (46)

Nope, he ran it stock, never added anything out of the ordinary.

Yeah the stock water seals are no good for this environment. 0W-40 Mobil1, all day everyday for me from this point on. I have heavy duty water seals and my bearings looked fine after using the Mobil1 so I will stick with it. Our motors were both remans, we both changed oil regularly, and had nearly the same mileage and we ran in the same environment, the only difference was the oil we used. Both our water seals were damaged but my bearings were not damaged and his were.

I depends where you live but my rules are:

1. never bang on it cold
2. use 40W or higher if you live in a warm environment
3. change it every 3,000 miles
4. if you run a sohn adapter use synthetic
5. watch coolant temps and shut it down if your coolant temps get in the 230F range

The specs will tell us a lot but for 40,000 miles there was some pretty good damage. His engine and my engine are just more proof that the mazda remans are sub par.

don_peppino24

iTrader: (1)

@9krpmrx8
1. as said, always wait for it to warm 10 min before slow drive, +10 before bashing it
2. i live in canada and only drive in the summer( mid-april - early november) but the weather is erratic from hot-cold so...
3. i do every 4000-5000 km
4. no sohn but considering it, but not any time soon
5. watch the temp like a hawk, especially when driving aggressively.


thanks for your reply

olddragger

iTrader: (3)

seems so--reman engines are not the best.
Thanks for posting these pics/etc.
One hint of something I am collecting data on and may be somewhat relavant to this thread is what do yall think the coolant temps spike too after you turn the engine off? And, should that be of concern?

nycgps

iTrader: (1)

it's called Reman for a reason. you get what you paid for

I wouldn't mind buying one and open it and see how "well" build they are tho ... *cough*

9krpmrx8

iTrader: (46)

I would imagine they do a bit because I know oil temps spike. I was reading oil temps from an adapter in the oil pan drain plug hole and when you stopped at idle after running hard the oil temps would rise up to 210F or so while idling. I never noticed coolant temps getting too high but getting to 220-230F was normal for me during the summer when we did runs up into the canyons. So I am sure that is what helped kill the coolant seals.

Rob at Pineapple said it appeared that the coolant seals in my reman got pinched due to not being installed correctly. He also said the housings were questionable and that he would not have reused them during a rebuild.