Originally Posted by Kafka

In Japan, they use 5W30.

In Speedsource Rx8, they used 5W20 in their race the whole time even though it is a Castrol Synethic sponsored race car...

There are numerous cases of synthetic engines still blowing up (most of them used car owner, so we don't know the history before they use synthetic), and engine rebuilder disassembling an engine for rebuild and found the 5W20 is lacking...

CONCLUSION: If you are still under warranty, I'd rather keeping the N.American spec. If you are out of warranty, do whatever that makes you happy!

Originally Posted by rotarygreg

josh, i never said anything about synthetic. That topic has been beaten to death and i just dont care to argue it. I myself will never ever ever use synthetic in my rx8. end of story. thats all i care to say about synthetic. Im talking only about weight.