I’ve noticed that Fuelly will frequently display anomalous fuel consumption (or mileage) figures for a given vehicle.
For example, a vehicle might consume 6.3 litres per 100 km on average and then show a best rate of, say, 2.1 litres per 100 km. A look at the data suggests that in these cases the individual forgot to reset the trip meter after the previous fill-up. Other times the anomaly is in the opposite direction and the high consumption rate (or terrible mileage) is likely the result of inadvertently resetting the trip meter (to zero), perhaps after several days of driving. Both of these problems (forgetting to reset the trip meter and inadvertently resetting it) are easily avoided by simply keeping track of distance travelled using the vehicle’s standard odometer when recording fuel-ups. For this reason, I recommend that when people join Fuelly they be encouraged to use the vehicle’s regular full odometer readings to keep track of distance travelled. (I suppose I would also recommend that the default setting for Fuelly be to track distance using the standard odometer readings instead of the trip meter.) There are fewer ways to get erroneous results that way.