How to calculate fuel economy per fill-up (full tank method)
Short answer: Fill the tank to full and write down the odometer. At the next fill-up, fill to full again. Fuel economy = distance driven since the last full tank ÷ fuel added now. Example: 612 km driven, 41.5 L added → 612 ÷ 41.5 = 14.7 km/L (6.8 L/100km).
Step by step
- Fill up until the pump clicks off. Note the odometer (say 48,200 km).
- Drive normally.
- Fill up to full again. Note the odometer (48,812 km) and the liters added (41.5 L).
- Distance = 48,812 − 48,200 = 612 km. Economy = 612 ÷ 41.5 = 14.7 km/L.
Converting units
- L/100km = liters ÷ km × 100 → 41.5 ÷ 612 × 100 = 6.8.
- MPG (US) = miles ÷ US gallons. 235.2 ÷ L/100km gives MPG US (≈ 34.6 here).
- MPG (UK) uses imperial gallons: 282.5 ÷ L/100km (≈ 41.5 here).
What if I did not fill to full?
A partial fill cannot give an exact figure for that stretch, because you do not know how much fuel is left in the tank. Keep logging it and add its liters to the next full-tank calculation: economy = distance since the last full tank ÷ all fuel added since then, including partial fills.
Why one reading looks strange
Pumps click off at slightly different levels, so a single stretch can be off by 5 to 10 percent. Look at the average of several full tanks. A missed fill-up in your log will make one stretch look much worse.
Let the app do the math
In Odonote you enter only the odometer and total cost; add liters if you have them. Tick Full tank and the economy for that stretch appears right after you save, in km/L, L/100km, MPG or km/kWh.