Difference between car oils

My Mazda RX-8, only takes a Dexelia Ultra 5W 30 which is a mineral based car oil. is it true that this is better than synthetic oil for High Performance engines? If so, why?

No, it’s not true. As a matter of fact many high performance engines require synthetic oil, particularly those with turbochargers. Turbos are driven at high speeds by the hot exhaust, and they subject the oil to higher temperature stresses than regular engines.

Mineral oil and synthetic are the same chemically, except tha synthetic has more consistant molecular size and fewer impurities. Www.carbibles.com has a good primer on oils, and the API (American Petroleum Institute) website has good information. I recommend a visit to both.

Having said that, continue to use only what’s recommended in your owners’ manual. Don’t try to second guess them.

Is that the oil recommended in the owner’s manual?

It’s hard to believe Mazda specifies a brand of oil for their rotary engine. When I had my RX-7 I could use any brand as long as it was the correct viscosity.

I’d follow the recommendation in the owner’s manual, whatever it is.

I’d think any good synthetic would meet or exceed the specs, but the owners manual is what to believe if you want the warranty to be honored.

If you have a rotary engine, I suppose it’s possible that the oil that they specify has an additive package that is meant to keep the seals on your unusual engine in good repair.

I searched on line and it appears that Dexelia Ultra is marketed by Mazda. This is similar to Honda’s recommendation to use only their branded fluids and no other. You might void the warranty if you use anything else, but if you check around on line, you should find other RX-8 owners that use similar oils from other manufacturers. Total Oil manufactures it for Mazda in Europe. Snoop around here for information: