Adding a partial to the next fill-up.

[pb]

Fuelly is using a full tank as a baseline for individual fuel-up MPG calculations. If you combine fuel-ups this way I think you'll find the MPG calculation will either be too high or low compared to your normal fuel-ups because your "tank size" will be too big.

It shouldn't impact your overall MPG because partials are counted there. But you'd be trading the no MPG calculation of a standard partial for a fairly inaccurate calculation. And you lose some accuracy in recording how you really fueled-up. So I'm not sure what the advantage of doing it this way would be. If it works for you though, that's ok.