freash spark plugs make a big diff as well . and play with tire pressures . and as my cars got everything in the running gear warmer through the race day , they got quicker as well .
That leads me to a question. My engine builder told me to run 20/50. I do realize that a loose engine may require a heavier oil but I was thinking of 15/40. As long as I have oil pressure at idle I should be good right ?
