I've noticed that the NASCAR people generally use a 5 gallon oil tank while Sprint cars look like they're using something closer to half that. That started me wondering if there's a calculation or rule of thumb for deciding what the volume of the tank ought to be. Do you start with the volume normally used in a wet sump system, deduct for the difference in the volume of a dry sump versus wet sump oil pan, add in the amount held in the lines and cooler and come up with a figure that's an equivalent to the original wet sump, or do issues like race duration and governing body rules come into play?