When I used to race the shell series (QLD) in the late 90's, I ran Silkolene comp 2 plus & Shell 98 @ 40:1. I ran the whole series + practice sessions without A freshen up.When I pulled the motor down,the piston had A nice little tan burn pattern & the piston / ring were still well within servicable tolerances.Most of the oils these days are good, but you can guess what oil I still use...