With the oil consumption of the RX8, think it is safe to use oil additives such as Prolong. I emailed prolong and got this response:

This question has gone back and forth but I was told by race car engine rebuilders that they use prolong when they start up a new engine. It does not hurt the new engine.

I am not sure that this addressed my original question of it being safe in the rotary and if it contains any synthetic additives.
I could use any feedback available. Thanks

 

Most additives are a joke.

 

Oil additives are usually designed for old worn out piston engines. The RX-8 engine uses a new design feature for the side ports, a cut-off seal below the side seals. This seal is exposed to exhaust gas carbon and any ash from the burning fuel and oil. You could end up causing it to stick with burnt additive ash

Prolong and many others are based on a very old (ww II) extreme pressure additive that isn't needed in the rotary. A good low ash mineral or synthetic oil is all you need but some synthetics have a lot of ash forming additives for diesel use.

 

Oil companies spend millions of dollars to research and refine their formulations - don't go screwing it up, its not going to get any better!