Fuel Economy Converter

Frequently asked questions

Why is US mpg lower than UK mpg for the same car?

Because a UK gallon (4.54609 litres) is larger than a US gallon (3.785411784 litres), the same car travels more miles per UK gallon. To compare, 30 US mpg is about 36 UK mpg, or roughly 7.84 litres per 100 km. Note that litres per 100 km is an inverse measure: a lower figure means better economy.

How do I convert L/100km to mpg?

Divide 235.214 (the US conversion factor) by the L/100km figure to get US mpg. For UK mpg, divide 282.481 by the L/100km figure. So a car rated at 6 L/100km is roughly 39.2 US mpg or 47.1 UK mpg. This converter does all three conversions at once when you enter any unit.

What fuel economy is considered good for a petrol car?

As a rough guide, under 7 L/100km (over 40 US mpg) is considered efficient for a petrol car, 7 to 10 L/100km is average for a mid-size car, and over 12 L/100km is on the high side. Diesel cars typically show 10 to 15 percent better economy than equivalent petrol models.

Why does fuel economy change between highway and city driving?

City driving involves frequent acceleration from low speeds, which consumes more fuel per kilometre. Highway driving maintains a steadier throttle position, so the engine runs closer to its efficient operating range. Most manufacturer ratings include a combined figure weighted about 55 percent city and 45 percent highway.