Switched to 5W-30 from 0W-20

[Mazdiod2]

Sounds like a car from the '80s. I haven't seen any of that kind of stuff for years. As far as Castrol, it seems unlikely that Mazda would recommend it in the owner's manual if it was a problem.

 

[JDM_CX8]

I think the high moly gig is over rated...I'm betting they only specced the high moly as the 0-20 was so thin that it needed everything thrown in it to actually lube the motor....no such issues for the 5-30 so moly is not a required factor

 

[dunhillmc]

I think the high moly gig is over rated...I'm betting they only specced the high moly as the 0-20 was so thin that it needed everything thrown in it to actually lube the motor....no such issues for the 5-30 so moly is not a required factor

Toyota, Honda, and Subaru all use high moly oil for their 0w-20 factory fills. I think it's the same Idemitsu oil for all of them. The 0w-16 and 0w-8 Toyota now specs are also very high in moly

 

[N7turbo]

Yup. Toyota is using it on their low viscosity oils because they need it. The 5-30's don't need it.