How to care for RX-8 (rotary)? Proper oil?

[blackman777]

I am shopping for a Mazda RX-8 but reading a lot of horror stories about the rotary engine:
- never use synthetic oil
- buy lots of oil because the engine consumes a quart every 1000-2000 miles
- the seals often "blow out" and need replaced

Anybody have recommendations on what proper Oil to use in this finicky engine? The manual says 5w-20 but I'm thinking a thick 5w-40 might be better to reduce consumption? (Not Mobil 1 as it's synthetic.)

 

[Dominic]

IIRC the rotary motors have an oil injector and oil consumption is actually a part of their operation. Enjoy the motor and just check the oil and add as needed.

I wouldn't change grade, but perhaps use a good quality recycled oil like Valvoline Nextgen Maxlife. At least then you're consuming a recycled oil, which is slightly more eco-friendly - and you get maxlife benefits to keep the engine in good shape.

I'll be interested in what some of the more knowledgeable people in this thread suggest to you that are RX8 owners.

 

[Flareside302]

Yes do not use synthetics.. They do typically consume 1 qt every 1k-1500 miles depending on how high mileage they are. The seals your hearing about is the Apex Seal. Look it up and read..

Also they typically KEYWORD TYPICALLY need rebuilds every 100k or so

 

[chubbs1]

I would stay with the grade as there is no 5 or 10w40 that does not contain at, least what is legally, called synthetic components. So I would use a conventional 5w20 just as recommended.

 

[fdcg27]

FWIU, this engine needs to be run hard.
Therefore, you have good reason to redline it often.
What a shame!

 

[blackman777]

I've heard the "run hard" advice but it makes zero sense to me...... it just means the seals wear-out faster. Right? I have my doubts the automatic redlines the engine much (instead choosing high gears to spin it more slowly).

 

[Flareside302]

Foot to floor will get if wound up!

 

[silverrat]

Automatic for an rx8 is a mistake

 

[fdcg27]

Originally Posted By: blackman777
I've heard the "run hard" advice but it makes zero sense to me...... it just means the seals wear-out faster. Right? I have my doubts the automatic redlines the engine much (instead choosing high gears to spin it more slowly).


Which explains the reason that stick rotaries are known to last longer than automatics.
It isn't seal wear that's the problem. Rather, it's the acumulation of deposits around the ports with moderate running, which will break the seals.
This is an engine that needs to be used.
It won't last 200K either.

 

[kyoo]

There's a big thread on this on the rx7 forums - yes it consumes oil by design. the reason they say no synthetics is due to the ? as far as how a given synthetic will burn once injected. sigh.. such a finicky engine

 

[QuOk]

Drive it like you stole it will prevent a lot of the problems.

 

[yonyon]

You do seem to understand what you may be getting into. Before you go out and buy an RX-8 it would be a good idea to talk to someone who's had one for a few years. If you treat it like a "normal car" you will not be happy.

 

[jrustles]

I'd use a synthetic oil, because the "synth is bad" thing is such an unsubstantiated old wives tale. Most "synthetic" isn't even "synthetic" but petroleum based, only cleaner than grII, so we need the extra contaminants for what reason, again?

When people cite volatility and that "synthetic wont burn properly", guess what... the only thing burning 'more readily' in GrII vs GrIII is the lighter junk and volatile components, ie aromatics, polymeric viscosity additives. The heavy components of both 'synthetic' and 'conventional' oil of a given grade should oxidize equally well, only the GrIII is more pure, with less junk that either oxidizes and catalyzes oxidation at lower temperatures than the GrII.

If GrIII wouldn't burn properly, then neither would the heavier components of a grII, and liquid oil would be flooding the combustion chambers. (Protip: that's ludicrous and doesn't happen)

My perfect rotary oil, at this point in time, isn't even a GrIII, but a GTL oil with "custom built" HC chains. I'm talkin' bout Pennzoil Ultra 10w30, that should burn the absolute cleanest of anything you could buy, and cleaner burning means less deposits to form around the seals, like a conventional oil will do. Combined with 2T premixed fuel, or conversion to dedicated 2T oil injection and that setup should have the rotary bulletproofed and ready for a long life.

Choose wisely my friend

 

[CATERHAM]

Originally Posted By: jrustles


I'm talkin' bout Pennzoil Ultra 10w30, that should burn the absolute cleanest of anything you could buy, and cleaner burning means less deposits to form around the seals, like a conventional oil will do. Combined with 2T premixed fuel, or conversion to dedicated 2T oil injection and that setup should have the rotary bulletproofed and ready for a long life.

PU is a relatively clean burning oil but it certainly isn't the cleanest in terms of deposits in the TEOST 33 (ASTM D6335) test.
The cleanest API oil I know of is Castrol Edge 5W-30.

 

[901Memphis]

The cars consume oil, so it's a good idea to allocate space in the tiny trunk for a jug or multiple quarts of oil. Also drive it like you stole it will help from everything i have ever read on the RX8.

Caterham is right about the Castrol Edge 5w30 leading in the lowest deposit score, Amsoil is another top choice, but that could get expensive.

Probably since it's going to get replinished a lot , maybe something like an Ashland product, such as Valvoline conventional. Synpower did well in the deposit test, maybe the conventional would do well too.

You can always get the Mazda 0w30 for the rotaries.

Being as this is an oil forum, i would advise you to look for another car, as you may not get very much life out of a used RX8 which already likely has half of its engine life used up... Unless you have the cash for a rebuild, in which case go for anything and beat it til it needs rebuilt.

 

[jrustles]

Originally Posted By: CATERHAM

PU is a relatively clean burning oil but it certainly isn't the cleanest in terms of deposits in the TEOST 33 (ASTM D6335) test.
The cleanest API oil I know of is Castrol Edge 5W-30.


Ah yes, Edge came out on top in AMSOILs 5w30 tourney and would agree that Edge would make an excellent choice particularly for the Ti AW additive for all of the ferrous sliding surfaces in the rotary engine.

The TEOST test relevance in this case, I'm not sure can be related to the combustion of extremely dilute solutions of oil reduxed into the af mix. D6335 is really a slow, thermo-oxidation deposit test, where oil samples are doped with a catalyst and cycled in an unrealistically extreme turbo simulation. TEOST is akin to HTO-06 in scope. I believe thermo-oxidative deposit performance on 33C can be increased via certain additives and using low-polarity base oils. Who can imagine how horribly 2T premix oil would perform on the TEOST

By pure, I'm referring to the HC purity of a paraffin based oil, an inherent quality that by definition cannot be achieved by additives

 

[blackman777]

I see the 2009 engine was redesigned with additional oil injection ports.
Maybe that's the model I should choose (for longevity).

 

[Nederlander75]

There was much more to it than that and yes the 09-11's are lasting much longer. There have been some 09's fail but I think that is related to the very early versions still getting the SI (04-08) shorter side seals.

 

[AHC]

Use the spec viscosity and no syn from what I've read

 

[Clevy]

I remember a guy with an RX-8 with some total quarts he wanted to trade for castrol gtx,quart per quart.
He said something about it leaving no deposits behind on the apex seals when it gets inevitably consumed.
That tells me a lot. If a guy is ready to trade really good syn for vanilla castrol that's what I'd be using.
I saw the thread he last year iirc.