True MPG: best coupes, convertibles and sports cars 2018

What Car?'s True MPG tests show what you can really expect from a car. Here we reveal the most efficient coupΓ©s, convertibles and sports cars we've tested so far

Words By Steve Huntingford

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The mpg figures published in sales brochures can be one of the main reasons for choosing a particular car, but those results are often misleading. Fortunately, What Car?'s True MPG tests reveal what sort of fuel economy you can expect in the real world.

To ensure accuracy and repeatability, our tests are conducted under strictly controlled laboratory conditions but based on a real route that takes in urban, A-road and motorway driving. After all, even if economy isn't your top priority, it's useful to know how much you can expect to spend on fuel.

Below, we count down the most efficient coupΓ©s, convertibles and sports cars we've tested so far.

Best real MPG coupΓ©s, convertibles and sports cars

9. Mercedes S-Class Cabriolet S500

Official fuel economy: 32.5mpg; True MPG: 25.2mpg; Shortfall: 22.5%

We named the S500 Cabriolet the best convertible for more than Β£35,000 at the 2017 What Car? Car of the Year Awards, because it has a stunning interior and can transport four people in absolute comfort. It’s even capable of slightly more than 25mpg in real-world driving which is decent given the car’s V8 engine and colossal weight.

Read our full Mercedes S-Class Cabriolet review

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8. Porsche 718 Cayman 2.5 S

Official fuel economy: 34.9mpg; True MPG: 28.4mpg; Shortfall: 18.7%

Porsche recently swapped the naturally aspirated flat-six engine in the Cayman S for a turbocharged four-cylinder unit, with the aim of improving efficency, and the result is a True MPG of 28.4. True, the Cayman S doesn’t sound as good as it used to, but in every other respect it's a staggeringly good sports car.

Read our full Porsche Cayman review

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7. Jaguar F-Type CoupΓ© V6 auto

Official fuel economy: 33.6mpg; True MPG: 28.8mpg; Shortfall: 14.3%

Impressively, the F-Type is more efficent than the Cayman S, despite having a big 3.0-litre V6 in place of the Porsche's 2.5-litre flat-four. The F-Type also offers catwalk looks and makes a great noise, but it doesn't handle as well as you'd hope and the infotainment system is woefully outdated.

Read our full Jaguar F-Type CoupΓ© review

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