what is fuelly average based on?
 

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.

hope that makes sense. thanks in advance.

MPG is calculated per gallon. Miles per gallon. There's no cheating. It's literally just all of the miles you've driven divided by all of the gallons you've used.

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.

There's no average of the averages calculations if that's what you're asking.
As BDC stated exactly.

Although its important to remember on your dashboard, running MPG is displayed, thats the average from your last 10 tanks, that will vary alot depending on seasons etc :)