Originally Posted by Sleepy-z

Well if it matters we use 5w-20 for the rebuilt engines, non synthetic and I know for a fact that the first race the Mazdaspeed RX8 ran with the castrol synthetic sponsorhip and won the daytona 24hr in last they used non synthetic.....you didnt here that from me. I dont know what they are running now in the engines for mazdaspeed, they probably ran some tests on it this year, who knows I haven't seen them since late last year though. Personally my only opinion on it is from what I understand the engine should burn oil and synthetic is designed to not burn up as easy so I dont know if thats the best combonation but then again as I said I dont know too much about whats best I just go by the books.

Originally Posted by 01Racing

There is also a different internal oil seal you have to use if you want to run synthetic oil. I dont know why this converstation keeps coming up lol, we all know you arent supposed to use synthetic oil in a production rotary engine.

Originally Posted by 01Racing

There is also a different internal oil seal you have to use if you want to run synthetic oil. I dont know why this converstation keeps coming up lol, we all know you arent supposed to use synthetic oil in a production rotary engine.

Originally Posted by http://www.royalpurple.com/faqs-rotary.html

Mazda makes a statement in the Owner’s Manual not to use synthetic oils in a rotary engine, why do you say that it is OK?

Royal Purple has performed seal compatibility testing on the components used in a rotary with excellent results — including older rotary engine seals dating back to the Cosmo. Royal Purple’s Technical Services Manager David Canitz (who has been an owner and racer of rotary engine cars using synthetic motor oils since 1985 with excellent results) has been trying to find an answer to this Mazda statement for the last 18 years.

In the early development of synthetic oils decades ago, there were purportedly some seal compatibility issues. Today’s synthetic oils do not have the compatibility issues of the old oils. There is no substantiated evidence of seal compatibility issues with Royal Purple.


Will the synthetic oil affect the oil seals?

No. Royal Purple’s motor oil is fully compatible with the elastomers found in rotary engines as well as more conventional piston engines. The oil seals, housing seals and other elastomers used in rotary engines typically consist of Buna N, Nitriles, Neoprene or Viton materials, which are also commonly found in piston engine cars.