1. The problem statement, all variables and given/known data What i am trying to do is calcuate the miles used in my car driven a certain distance. 2. Relevant equations What i did was take a GPS unit that takes my position and tracks where i drive by the easting, northing, and alt. I then can put that data on a computer and anlyze it. But my final number is alot better than the number at get at the gas pump. So i think i am forgetting to calcuate something and was hoping you guys could help me. I fill up everytime time after i track my position and i can not seem to get that number in the computer. 3. The attempt at a solution i have time, x (easting), y (northing), z (alt) for my known data then i am calucating speed, accleration, net force, power and then i take the absolute value of power to get work. Then i take my work value and divide it by 132000000 which is 1 gallon of gas in joules. Which gives me the amount of gas used by the car. I can then divde that number by .1 since the motor is 10% eff. i get a valule of 4.71 at the gas stattion on the computer i get 2.974 Which i know the computer value is high since my car only gets about 18-20 mpg. (99 miles driven) Looking foward to hear how i can better calacuate the number closer to the gas pump amount.