I am curious as to how long you guys go between oil changed? We, myself and an E Prod driver, change oil every 8 heat cycles.

We have always used 20w/50 mineral or 15w/50 synthetic wt oils from Valvoline and Mobil 1. Both seem to be fine in terms of heat and pressure. On recomendations from several engine builders - Tony Riveria, Jesse Prather - we don't use low viscosity oils.

Regarding increased ZDDP levels, I can certainly see the value for an oil the contains zinc in a solid lifter piston engine. I wonder if there would be the same concern/value in a rotary engine. I can't really think of a bearing surface in a rotary that is similar to what you have with a lifter and a cam lobe. Where do you guys see the value in ZDDP??