True MPG: most and least efficient cars revealed

What Car?'s laboratory tests use a real-world driving route to show what fuel economy you can really expect. So, what are the best and worst performing cars?...

What Car?’s True MPG real-world fuel economy figures show what sort of efficiency you can really expect from your car.Image 1 of 22

Tests are conducted in a laboratory to ensure repeatability within 1%, but they are based on a real-world route that takes in town, rural and motorway driving.

The results reflect what's achievable if you’re driving gently and sticking to speed limits, but aren’t resorting to any unrealistically slow acceleration or special 'hypermiling' techniques.

True MPG is not only fully reflective of real-world performance; it is also much more realistic than the official government fuel economy figures that car manufacturers have to quote.

The True MPG tests are carried out under tightly controlled conditions: climate control is always set to 21deg and cars due to be tested are stored overnight at a set 23deg so they all start with exactly the same engine temperature and in the same ambient air temperature.

In this slideshow, we reveal the 10 most efficient cars we've tested so far – and the 10 that used the most fuel.