The fuel cost of a journey depends on three factors: distance, your vehicle's fuel consumption rate, and the current fuel price. The formula is straightforward:
Fuel cost = (Distance × Consumption per 100 km) ÷ 100 × Price per litre
For example, a 300 km trip in a car that uses 7L/100km with fuel at $1.60/L: (300 × 7) ÷ 100 × $1.60 = 21 litres × $1.60 = $33.60.
| Vehicle type | Typical consumption |
|---|---|
| Small city car | 4–6 L/100km |
| Family sedan | 6–8 L/100km |
| SUV / 4x4 | 8–12 L/100km |
| Large truck / van | 12–20 L/100km |
| Hybrid car | 3–5 L/100km |
| Motorcycle | 3–5 L/100km |
The official consumption figure for a vehicle is measured under controlled conditions and almost always differs from real-world usage. Key factors that increase consumption above the official figure include motorway driving at high speed (above 110 km/h, fuel use rises sharply), stop-start urban traffic, air conditioning (adds roughly 0.5–1.0 L/100km), carrying heavy loads, cold weather (cold engines are less efficient for the first 5–10 minutes), and under-inflated tyres (each 10 PSI below recommended pressure adds about 0.3% to consumption).
Conversely, smooth driving at moderate speed, warm weather, and a well-maintained engine can bring real-world consumption close to or below the official figure.
For a 15,000 km annual mileage at typical European fuel prices in 2025: a petrol car averaging 7L/100km at $1.70/L costs approximately $1,785 per year in fuel. A diesel car averaging 5L/100km at $1.65/L costs approximately $1,238. A plug-in electric vehicle averaging 18 kWh/100km at $0.25/kWh costs approximately $675 — roughly 38% of the petrol cost, though the comparison changes significantly if charging is done on public fast chargers rather than at home.
Multiply distance by your vehicle's fuel consumption per 100 km, divide by 100 to get litres used, then multiply by the price per litre. For a 500 km trip in a car using 8L/100km at $1.60/L: (500 × 8 ÷ 100) × $1.60 = 40 litres × $1.60 = $64.
Multiply the distance by your fuel consumption rate and divide by 100. A 200 km trip in a car using 6.5L/100km uses 200 × 6.5 ÷ 100 = 13 litres.
Official fuel consumption figures are measured under ideal conditions. Motorway speeds above 110 km/h, air conditioning, cold starts, and heavy loads all increase real-world consumption above the official figure by 10–30%.
Most modern petrol cars consume between 5 and 8 litres per 100 km in mixed driving. SUVs typically use 8–12L/100km. Hybrids average 3–5L/100km. Diesel engines are typically 20–30% more fuel-efficient than equivalent petrol engines.
Divide 282.5 by the mpg figure. For example, 40 mpg = 282.5 ÷ 40 = 7.06 L/100km. To go the other way, divide 282.5 by the L/100km figure.