Filling oil, Synthetic or Non Synthetic??
 

I've read up on filling the oil on our 8. Some say it's ok to fill it with Synthetic and some say it's a big nono. I just want to know which one is actually right. Some shops offer only 5W20 only in synthetic by Pennzoil of which I brought already without seeing it's actually synthetic. I've read that most people use the Castro brand 5W20 and swears by it. Some actually use Royal Purple, which I haven't seen anywhere. Can somebody point out which oil is the best to use so I can go out and buy a couple of boxes or something? Thanks

This topic has apparently been highly discussed. My dealer told me NOT to use synthetics. I did a search on here and here's one of the latest statements..

Personally, my oil changes will be performed by my dealer for the foreseeable future. :)

Cheers!

I have talked to a local shop that specializes in Rotary engines. They have been using synthetic for years (RX7 and now RX8). They have not seen any problems. But they agree that if I am going to be changing oil every 3k miles (which I am) it does not make much difference.

This shop has been around for many years now. They prepare Mazda race cars and street cars (Miatas, RX7 and RX8). Here is what they use/recommend (based on their testing):

Idemitsu 20w50 Rotary synthetic oil
Red Line MT-90 75w90 synthetic transmission fluid
Red Line 75w90 synthetic gear oil (for the differential)
Motul 600 hi-temp brake fluid

The 2nd thread (a sticky) in this forum is wholey and soley on this topic
https://www.rx8club.com/series-i-tech-garage-22/cumulative-synthetic-oil-discussion-52856/

The rating on Synthetics oils supposedly isnt as important as mineral oils. For mineral oils, you are supposed to keep the W and normal number as close together as possible as that the bigger the difference, the more additives added which means less oil. With synthetic oils its an inherant part of the materials that make up the Oil.

Anyways, have a read of that thread, its good reading.

Andrew