Wrong MPG Calculations

[bates]

richardharo, Fuelly is designed to calculate your fuel consumption and mileage based upon fill ups, not partials. It sounds as though you are expecting Fuelly to calculate your mileage based upon partial fill ups which is mathmatically impossible. Fill your tank and reset your trip meter or log your odometer reading. Then drive until your next fuel stop, fill the tank again and record your trip meter or odometer reading. The number of miles driven between fill ups divided by the quantity of fuel added is your mileage for that tank. Reset your trip meter and continue to drive, refuel fully, log your miles driven, and repeat. This will yield your fuel economy in a meaningfull manner. Partial fill ups don't work because there is no way of telling how much fuel was consumed between partial fill ups since the tank didn't start out full and end full thus giving a fixed quantity of fuel consumed.