Had been running 33. This weekend tried 35, engine temp came up quicker which is good and egt dropped slightly to 1100 picked up acouple of hundreds to 330,but hard to compare as it was 95 degress and marginal track. Then went to 37,engine temp up noticeable and egt way up,1250/1300. So I will probably stay at 34 which is about the same as is i was running gas.I parked next to a super comp olds running off the stop 8.30,says he never goes above 35,this is a 622 chevy.I am only at 440 cu,around 775 hp,15/1 720 roller,so the answer is eeach engine has different needs based on a lot of factors ,i would be conservative and err on the side of caution.