Originally Posted by RIWWP

Keep in mind one fact: Your stock oil system is trying to use 1 oil for 2 entirely different jobs:
1) Lubricate the e-shaft bearings (High pressure, high heat, high sheer environment)
2) Cool and lubricate the side seals (No pressure, incinerating heat, low sheer environment)

No, the viscosity of the oil that you inject into the housing to cool the side seals has no impact on how long the side seals or apex seals last. The fact that it is dirty 4-stroke is FAR FAR FAR more harmful to the seals than the viscosity or type.

If you want to help make your seals last longer, then convert to injecting only clean 2-stroke oil via a SOHN adapter. 2-stroke oils are designed to lubricate even as they are burned off. 4-stroke is not designed to be burned at all.

The type and viscosity of oil in your engine only really matters for the bearings on the e-shaft, with the sheering and stress that it sees. For that, our engines are closer to diesel engines in how abusive it is on the crankcase oil. Diesel oil actually does well, although if you use it with a cat in your exhaust it will kill your cat quite fast. Synthetics hold up better than non synthetics.

Synthetic Mobile 1 0w40 has consistently had the best oil analysis results from members here.

Originally Posted by RIWWP

Old piston engines can have a problem with it, as it will tend to increase oil consumption as the synthetic will react differently with the sealing. Not a problem with the rotary, as we inject it to burn anyway