WebToolArcPractical guide and verification
Use the tool first, then use these checks to interpret, verify and hand off the result without displacing the primary workflow.
Use one complete fuel interval
The most reliable fill-up calculation uses distance driven and fuel added over the same interval, ideally between comparable full-tank states. A partial fill or an odometer interval that starts before the measured fuel can make the MPG look better or worse than the vehicle actually achieved.
Compare like-for-like history
Saved results become useful only when the measurements are reasonably comparable. Note unusually cold weather, towing, heavy traffic, tire changes, route mix, or a partial fill before treating a trend as a vehicle change. The new history view summarizes the measurements; it does not diagnose why they moved.
Use both MPG and L/100 km correctly
MPG is distance per unit of fuel, so higher is better. L/100 km is fuel per fixed distance, so lower is better. Because one is the reciprocal of the other, averaging converted values independently can produce different-looking summaries. Keep the original measurement basis when comparing a sequence.
Export evidence before drawing a conclusion
A CSV of saved fill-ups preserves the date, distance, fuel amount, units, MPG and L/100 km so you can inspect the trend in a spreadsheet or keep it with maintenance records. Treat a small sample as preliminary and verify major changes with repeated measurements before making a repair or efficiency claim.