Im using 10w30 right now but I'm switching back to 5w30 this week when I change it since i'm moving out of FL and don't feel I need that thick of oil up North....

 

I use a mixture of Castrol GTX and Mobil 1 whichever is available. Lately I saw some sale on Castrol Syntec so I picked up 2 jugs.

 

Most FD and TII owners up north run 20w50 in the summer months and 10w30 in the winter months. That'd probably work out nicely in the 8, running 10w30 in summer and 5w30 in winter.

 

Why not just stick with the 5w30 full stop?!

 

5W-20… 5W-30… I doubt it's critical. Far more important that you check oil level every other fill up, add oil as necessary, and change it regularly.

My guess is that the 8 has a lower tolerance for forgetting these things than cars powered by ordinary engines. And that 8s that develop engine problems develop them mostly from owner neglect or misuse (i.e. not changing oil regularly, not checking the level frequently, not redlining the engine regularly, modifying the engine, using synthetic oil, dumping additives into the fuel tank).

FWIW, assuming most US RX-8 owners are not on this forum, the vast majority of 8s in this country are running 5W-20.

 

Among the rest of the recommendations, I'm surprised nobody has mentioned that whatever you use, make sure it's rated API Service SL (or is it SM? check the manual) and/or ILSAC. Look for the API label on the bottle. There are some oils that advertise that they meet or exceed the API rating, but are not actually certified.

Ken

 

Idemitsu Japan does make 5w-20. but its not their RE(Rotary engine) oil, its listed as motor oil.

in japan they use 0w30 as factory Rotary fill, of course its Synthetic (no conventional oil can go 0w)

and Mazda Japan sells Synthetic motor oil thats PAO based, probably Idemitsu rebrand.

the clearance for 13b-msp is tighter, but heavier oil will flow just fine.

Im a maintenance freak and my motor still failed, 0-5K miles 5w20, 5K - probably 48303 miles 5w30. and dont forget, your motor might be dying and it will run just fine till it dies one day.