Partial fillup wrong MPG
 

I have noticed that Fuelly does not correctly calculate MPG after partial fillups. Here is an example screenshot. I have a full fillup, followed by two partial fillups, followed by a full fillup. The last fillup ignores the partial fillups in the MPG calculation. Instead, it should do (170,148 - 169,700) / (9.220 + 1.467 + 1.751) = 36.0 MPG.

By the way, the reason for this situation is a friend put gas in the car and saved the receipt for me, but did not write down the odometer, so I just entered the previous value.

Okay, I've come up with a workaround. If I change the odometer readings to 169,701 and 169,702 then it calculates the next fillup correctly.
The first thing I tried was leaving the odometer blank, but that didn't work either. I suggest fixing the app so that a blank odometer reading calculates correctly.

Interesting follow-up to this six years later.

If you put a real odometer value on a partial fill-up entry it incorrectly calculates the net MPG using the mileage difference between the recent full fill and the preceding partial fill... yielding a poor MPG result.

The workaround/fix is to leave the partial fill's odometer value blank, which the system then automagically populates with the previous entry's odometer value.