usually (=always) take full 40 gallons on all but last pit stop and I
generally use turbo setting 6. Computer cars seem to use similar
tactics in ovals, although it looks like they take 35 gallons or use
higher boost in Michigan.
BTW: Computer drivers do crash sometimes without my assistance. I have
a replay where AI-Nigel Mansell (1994 car set) loses it in Michigan: Alone
in the turn 3-4, heavy oversteering, lots of smoke and airborne right
side wheels;-)