Yet another 5W20 oil usability question - Mazda Rotary Engine

[shocar]

The Mazda RX-8 is sold worldwide. It comes with a "high power" or "low power" engine option. The high power engine has more intake air flow (more ports) and is rev-limited higher than the low power engine. The low power engine is the same displacement and compression ratio as the high power engine. The peak torque is slightly higher with the low power engine.
The low power engine is used with the automatic transmission option. In every locality except North America, the high power option has one engine oil cooler used. In North America, 2 oil coolers are used. Worldwide, the low power option uses one oil cooler. In the US, Mazda specifies that 5W20 oil be used with both the low and high power engines.
Does this information provide a "data point" on the thinking of the Mazda engineers with respect to the use of 5W20 oil? Does this information show an operational limit problem which was solved to enable 5W20 to be specified with the high power engine?
Should our thinking be rather that any 5W20 problem solved with the use of an extra oil cooler would no longer exist because the Ford Spec 5W20 oil is so much better now?

 

[darkdan]

Rotary engines are strange things. Apex seals, can't use synthetics, etc and yada yada yada.

Plus, Mazda had to plan ahead and such to get it to pass emissions.

Searching google, I found this over at an RX-8 forum. Someone emailed Maxda about the oil and here is their response:

Question:
I keep hearing conflicting requirements for oil on the RX-8. I have personally heard from ppl that Mazda Service Dept's are saying different things when it comes to oil viscosity for the Renesis Engine. One Service Dept. says to use 10w30 oil in the RX-8. They said 5w20 is not recommended for the rotary, and the manual should be changed . He said to stop using 5w-20. Another dealer used 20w-50. We all know that the manual says 5w-20 for the American version. But The European version recommeneds 10w-30 in the owners manual. What
is true with all of this?

Answer:
In regard to your inquiry, Mazda does recommend using 5W-20 engine oil for your RX-8. Mazda recommends this lighter oil for all of our vehicles because it meets the corporate average fuel economy. However, using 10W-30 engine oil will not cause any damage to the engine. Please understand, Mazda does not recommend using synthetic oil for your RX-8.

 

[the_oil_dealer]

Want protection? Go for 10w30 or 15w40 HDEO. Simple as that. 5w20 is the new trendy oil, in a market when everything *but* engine logevity is an aspiration. Think HTHS

 

[Quest]

Japanese blender such as HKS,etc. all carries their special "house" version of rotary engine oil: most of them are around 10W40~15W40 and it's definitely mineral oil based.

I won't go with 5W20 in a rotary engine.

 

[DaveJ]

I played with the little twisting noise makers back in the 70s and 80s. We tried all sorts of oils. A bad one we found was Moble 1. The syn oils, after being injected dont mix with the gas well and the apex and side seals run dry and fail. I ran all mine that were oil injected on Delo 15W40. On many Dyno pulls there was only about 7 Hp differance between 5W20, 10W30, 10W40 and 15W40 on these angry bees. I did have a racer RX-2 with a RX-4 1308 that we removed the oil injector system and pre-mixed M1 Syn in with great results till it hit a wall at 130 MPH, not the oils fault. DaveJ

 

[unDummy]

If the oil 'cooling and capacity' is adequate, there is no problem with using a 20wt in the rotary engine.
Seems to me that Mazda did the right thing with the higher power US engine by including the 2nd oil cooler.
Lower power, less heat, leads to less cooling needed with the automatic cars.

I don't see rotary engines as strange, haven't seen the lack of lubrication or any problems caused by synthetics, and don't care for the anti-20wt or anti-synthetic hearsay/BS!

 

[DaveJ]

In my reply all my testing was done in the 70s and 80s when the oil was injected into the float bowl of the carb and was not mixed well. On all the newer fuel injected ones, its oil injection is better so any good oil should be fine, syn or dino. The only funny thing about rotery engines is the sound at 9500 RPM with a header and open pipes, 130+ DB @ 1 meter. DaveJ