We bracket race our car every weekend and often double enter. I have always ran NAPA brand type F. Nick and I drove my Roadster one night to the semi's and the win, with the time runs that was 17 passes in less than 7 hours. It only moved 2 numbers from 3pm to the finals at 10pm.
I guess what Im saying is if you run a good quality fluid, things should stay consistent for you.
And yes Nick was the winner and I bowed out in the semi's.