Calculating fuel consumption: method and practice
How to determine your vehicle's actual consumption
Knowing the actual fuel consumption of your vehicle is more valuable than the manufacturer figure. That is because the WLTP value quoted in advertising is measured under laboratory conditions and often deviates by 10–25% on the higher side in everyday driving. The formula is simple: consumption (L/100 km) = liters filled ÷ distance × 100. At 35 liters over 500 km, that works out to exactly 7.0 L/100 km.
For an accurate measurement, fill your vehicle to the brim and note the odometer reading. After a representative distance (at least 200 km, ideally 400–500 km), fill up again. Enter the liters filled and kilometers driven into the calculator. The longer the measured distance, the more accurate the result. One-off short trips (under 50 km) produce skewed values due to the cold-start phase.
Fuel consumption varies seasonally: in winter (below 5°C) it rises due to increased fuel demand during warm-up, cabin heating, heavier tires and cold engine-oil viscosity – by up to 20%. In summer, air conditioning use increases consumption by 0.5–1.5 L/100 km. Measured over a full year, this gives a more realistic annual consumption figure.
For your annual fuel costs, multiply your consumption by your annual mileage and the fuel price. At 7 L/100 km, 15,000 km/year and €1.80/L, that comes to: 7 × 150 × 1.80 = €1,890 per year. You can break this figure down in detail with our fuel cost calculator.