Synthetic oil rotary engine RX8?

Synthetic oil rotary engine RX8?
Mazda USA doesn't allow the use of synthetic oil for warranty support on rotary engines starting with the 2009 model year, it will void the warranty. Prior to that, they only recommended conventional oils; but, because they did not explicitly disallow synthetic oil in the owners' manual, they can not legally void the warranty for use of synthetic oils. That would violate the Magnuson Moss Act.


Japan, Europe and all other countries suggest synthetic oil.
Mazda in Japan sells group IV synthetic oil expressly for use in rotary engines.
Mazda's rotary racing teams run synthetic oil.

Rick Engman, who has built more race winning rotary engines than anyone in the USA does not recommend anything other than synthetic oil in rotaries.


The reason for the myth that you can't use synthetic oil in rotary engines is twofold. First, when they first came onto the market decades ago, the additive package included with early synthetic oils caused some elastomer seals to swell and fail. This issue has been resolve for a very long time. The second issue is how well particular synthetic oils mix with gasoline when injected into the engine to lubricate the apex seals, and how well and cleanly those oils burn off. Because Mazda N.A. does not have the research or legal budget to allow them to recommend some synthetic oils and not recommend others.