Fuel & economy
What a tank, a trip or a year of driving costs, and how to compare two cars.
Everything here rests on fuel economy, and fuel economy is the number most likely to mislead you. Miles per gallon is a reciprocal measure: the fuel saved by a five mpg improvement depends entirely on where you started. Ten to fifteen saves twelve times as much as forty to forty-five over the same distance.
That is why replacing the thirstiest vehicle in a household usually saves more than upgrading the most efficient one, even when the mpg gain looks smaller — and why litres per 100km, which is linear, is the better measure for comparing.
- Fuel cost What a journey costs in fuel, from the distance, the economy and the pump price.
- Fuel economy MPG to L/100km and back, with both gallons kept apart.
- Fuel savings What changing to a more efficient vehicle is worth over a year, and over five.
- Range on a tank How far a full tank goes, what it costs to fill, and the range worth planning to.
- MPG from a tank Work out what your vehicle actually returns, from a tank of fuel and the distance it covered.