Calculators · Fuel
Fuel savings and break-even calculator
A more economical vehicle often costs more to buy — a diesel over a petrol version, or a hybrid over a conventional car. These calculators show how far you need to drive before lower fuel costs repay the higher price, the fuel price at which two vehicles cost the same to run, and a direct comparison of running cost per 100 km.
Break-even distance for a more economical vehicle
Compares two vehicles with different consumption and fuel prices, and calculates the distance — and the number of years at your annual mileage — before the extra purchase price is paid back by fuel savings.
saving per km = (l₁ × p₁ − l₂ × p₂) / 100 break-even km = premium / saving per km
Fuel price at which two vehicles cost the same
Finds the price of vehicle B’s fuel at which both vehicles cost exactly the same per kilometre. If B’s fuel is cheaper than this, B is cheaper to run. Useful when diesel and petrol prices move apart.
p₂ = l₁ × p₁ / l₂
Running cost per 100 km
Puts two vehicles side by side on fuel cost per 100 km and shows the percentage difference. It is the simplest fair comparison when the vehicles use different fuels.
cost per 100 km = consumption × price
Worked example: diesel or petrol?
- Petrol version: 8.0 l/100 km at 1.50 = 12.00 per 100 km.
- Diesel version: 6.0 l/100 km at 1.60 = 9.60 per 100 km — a saving of 2.40 per 100 km.
- The diesel costs 2,000 more, so it pays back after 2,000 / 0.024 = 83,333 km.
- At 15,000 km a year that is about 5.6 years.
- If diesel rose above 2.00 per litre, the petrol version would become cheaper to run.
Break-even distance for a 2,000 price premium
| Saving per 100 km | Break-even distance | At 15,000 km a year |
|---|---|---|
| 1.00 | 200,000 km | 13.3 years |
| 2.00 | 100,000 km | 6.7 years |
| 3.00 | 66,667 km | 4.4 years |
| 5.00 | 40,000 km | 2.7 years |
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About these results
Results are theoretical estimates from standard engineering formulas. Real-world figures depend on conditions these formulas do not capture. Always follow the manufacturer's specifications for maintenance, loading and safety decisions.
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