what is fuelly average based on?

[satan]

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.