Flumoxxed or Bamboozled ? : On board MPG calc.

However it does it, the one in my Ford truck is pretty much right on. When pulling in for fuel I always check the computer for the fuel used value. Then I run the dispenser at full boar until the gallons get to within 1/2 gallon of the fuel used value. Run it slow and the final total pumped is within .1 or .2 gallon. Try it the next time, you'll be surprised.