www.RX7fb.com

The main problem is changing to Synthetic in the engine after it having been using Mineral for the past 30+ years, it has in the past been known to causing the housing seals to expand & cause to fail. As far as I am aware if used from start on a Rebuilt/New engine it is fine. I have always used mineral in all rotaries ever owned & also premixed @ 3-400 to 1.

This is generally not a problem with modern oils. The vast majority of modern oils have a very high compatibility with older seal compounds, and all seals used in rotary engines in RX7s are compatible.

I've always used mineral in a rotary, both turbo and N/a engines.... they were designed to run on mineral so that's good enough for me. It's more important to change it frequently.... you'll get better protection from some £14.99 mineral multigrade and changing it every 2000 - 3000 miles than you will putting £50.00 fully synth in it and leaving it for 20,000 miles.
When I used to restore and run Spitfires I used to use cheapo oil from B&Q and change it every 2000 miles and it came out as clean as it went in.
Maybe in FD's where the engine is more highly stressed there's a case for more advanced oils but 12a's have always seemed to run fine on mineral... in over 30 yrs of running these cars I've only had one engine give up on me and that was because it was a 90,000+ miler already on it's last legs and I bolted a turbo onto it and ragged it.

Oil is not something you should cheap out on !!!

Engine oil is cheaper than an engine repair/engine

Use cheap oil. You'll be doing repair alot sooner

You should be using 10w40 in UK

Preferably Castrol or something decent quality

Do not use cheap oil, like Halfords, Carplan, Tesco, etc

Oil system is the life blood of a rotary engine

I use Castrol edge 5w40 fully synthetic. Mazda oil filter. As I want my engine to last longer

6,000mls service/oil change max


If you have FC/FD/RX8 13B. A must is sold oil pellet to replace factory thermal oil pellet

manual says 20w50, I have been using total racing 10w50. 10w40 seems a bit on the thin side.

also 6k seems like a long service interval, I tend to only do 2/3k. I have an S4 13B from an FC so I did the thermal pellet bypass mod when changing front covers.

3000 miles max with filter change mid term & mineral/premix