Fuel economy comparison
When choosing between two cars, the sticker economy figure is abstract — what matters is the money you spend at the pump over a year. This tool turns each vehicle’s fuel economy into an annual running cost and shows the difference, so you can see exactly how much a more efficient car saves over your real mileage.
How it works
Pick a unit system, enter your annual distance and fuel price, then each vehicle’s economy. The tool computes yearly fuel cost for each car and subtracts to find the saving:
- MPG mode (miles, price per gallon): gallons = distance ÷ MPG, then cost = gallons × price.
- L/100km mode (km, price per litre): litres = (consumption ÷ 100) × distance, then cost = litres × price.
Because higher MPG and lower L/100km both mean better economy, the tool always identifies the cheaper car and the annual saving.
Example
Driving 12,000 miles a year at £6 per gallon, comparing a 30 mpg car with a 45 mpg car:
- 30 mpg: 12,000 ÷ 30 = 400 gallons × £6 = £2,400/year
- 45 mpg: 12,000 ÷ 45 ≈ 266.7 gallons × £6 ≈ £1,600/year
- annual saving ≈ £800
| Vehicle | Economy | Gallons/year | Annual cost |
|---|---|---|---|
| A | 30 mpg | 400 | £2,400 |
| B | 45 mpg | 266.7 | £1,600 |
| Saving | — | — | £800 |
All maths happens in your browser — your data never leaves your device.