been on fuelly for a while now, first time here on the forum. i imagine this question has been asked before but i have searched and couldn't find it so here goes.
does fuelly calculate a vehicle's average mpg based on mpg per tank or mpg per mile? i know that might sound confusing so let me break it down.
if fuelly calculates a vehicle's average mpg based on mpg per tank, i could fill up more often in warmer weather when mileage is better and less often in cold weather when mileage is worse. by getting more tanks at a higher mpg, i would have a higher average mpg even though i may have driven the same amount of miles in both cold and warm weather.
but if fuelly calculates a vehicle's average mpg based on mpg per mile, i would not be able to cheat like i just explained. this is because fuelly would see that even though i filled up 30 times in the summer getting 35 mpg and 10 times in the winter getting 25 mpg, i drove the same total amount of miles during each season.
i understand the concept of mpg. what i want to know is: does fuelly's tracking system add the mpg of each tank and then divide that by the # of tanks, or does it divide the TOTAL miles driven by the TOTAL gallons used? if it used the former system, 'cheating' would absolutely be possible.
i just tested this by calculating averages with both methods on a car on here. fuelly does indeed use the latter method, which is great. it's obviously the most accurate.