[thstone]

I have been trying to manage the weight of my Boxster Spec race car through the amount of fuel on board. Spec racing has a minimum weight of 2650 lbs with driver at the end of the race. Usually, the top 3 finishers are weighed immediately following a race.

Me and my car weighs about 2650lbs with no fuel, so I am trying to minimize the amount of fuel on board with the goal of having only 1 gallon left at the end of a race. Any additional fuel beyond the optimum amount is simply excess weight that is slowing me down.

This should be simple, right?

Thus far, this has been a massive failure due to the inaccuracies of the gas gauge. Not only is the gauge wrong, it is non-linear and not-repeatable, i.e., when the gas gauge shows a half tank, the number of gallons actually in the tank will vary.

Thus, based on this experience, anything less than an almost absurd dedication to detail and exact measurements of fuel used, distance driven, and engine load will be useless in determining repeatable MPG numbers to the accuracy needed to compare one brand of gas to another.