If only you could do the same with the average speed! I use fuelly.com to record my pathetic mileage, and knowing the average speed for each tankful would be a useful note to add for each entry.You can also set it up so that every time you reset your Trip odometer, the average MPG resets as well. Makes it really easy. After a fill up, just reset the odometer and your average mileage is back to nothing as well. All ready to go.