What is the best oil to use in a 89 n/a? is synthetic oil good or bad or does it even matter at all? pros & cons

 

rotary engine burns oil through the oil injection system which was designed to lubricate the apex seals. Synthetic oil was not designed to burn.

 

I would personally stick to dino oil to be safe. If you really want to use synthetic use a GOOD brand like royal purple, mobil one, amsoil, etc.

 

It doesn't matter. Unless you have a race car, synthetic oil isn't worth the money if you use it in the engine where it gets changed every 3,000-5,000 miles. However, synthetic oil is more economical in the differential and transmission where it will last 30,000-60,000 miles.

 

Interesting article that goes over some aspects not found in the typical discussions here. Obviously some bias, but grass roots motorsports has to lend some credibility.
http://www.grmotorsports.com/oiltech.html

They mention Containment of Contaminants which is certainly one that applies to rotaries. A friend of mine just finished Materials Engineering (BsME) and they learned in a corrosion & wear course this was a substantial benifit of synthetics. (anti-corrosion especially)

Another catagoy is Heat Removal. I've also heard from racing people their oil temps are lower running synthetics. Of course oil cooling is important in a rotary.

The ability to run spread of [cold]W[hot] viscosity is important too. Big wear occurs at startup. Running a lower vicosity oil produces a noticable difference in the sound of the engine when cold.

Synthetics aren't that much more than Casterol GTX. (although some would argue running a non-amsol synthetic means you have more carbon buildup)

I'm no expert, so that that for what you think it's worth.

 

That is incorrect. There is not one synthetic oil made that does not burn at or under 525F, with most burning around 425F and a considerably lower ash (what is left after the burn) than many conventional oils.

 

I didn't know that.

 

Older synthetic oils did not burn as well but I think that many modern day synthetic formulas burn very cleanly and still hold the positive aspects of synthetic.

 

www.racingbeat.com

If you want the best... Royal purple. Racing beat sells it at 8 dollars a bottle. According to Racing beat it is OK to use synthetic oils.

Quote from the RB site:

"Racing Beat has been recommending the use of synthetic oils in rotary applications for several years. Our research has found that synthetic oils provide superior friction reducing between sliding surfaces, reduced foaming, and lower oil temperatures."

They have alot of years working on mazda's so that reputation leads me to believe what they have to say.