True MPG: most efficient coupés, convertibles & sports cars

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, we use strictly controlled laboratory conditions, but the tests 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.

Here we reveal the 10 most efficient coupés, convertibles and sports cars we've tested so far – plus the one that used the most fuel.

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True MPG: 31.4mpg

The M2 is effectively a steroid-enhanced version of the BMW 2 Series. Under its bonnet lies a turbocharged 3.0-litre engine that pumps out 365bhp – enough for a 0-62mph time of 4.4sec with the standard six-speed manual gearbox.

Yet you can still get 31.4mpg out of the car when you drive it more gently.

True MPG: 34.4mpg

Both this entry-level version of the Cayman and the more powerful Cayman S swapped their flat six engines for turbocharged four-cylinder units back in 2016 in order to reduce fuel consumption and emissions.

The downside is that they no longer sound as special as they did.

True MPG: 34.9mpg

Fractionally more efficient than the Cayman is the BMW 430i Convertible.

That's despite it being much heavier with its four seats and metal folding roof.

True MPG: 39.8mpg

We've always rated the TT Roadster very highly.

This version's near-40mpg average fuel economy joins a list of attributes that also includes sharp handling and a gorgeous, high-tech interior.

True MPG: 40.4mpg

As good as the TT Roadster is, it's the hard-top version that we'd choose; indeed, no car has won more What Car? awards than the TT Coupé.

It's even better than the Roadster to drive and that bit more practical and efficient.

True MPG: 43.4mpg

There are more practical drop-tops than the Mini Convertible, because its rear seats are distinctly cramped.

However, with strong resale values and a True MPG figure of 43.4mpg, it still makes plenty of sense.

True MPG: 44.2mpg

The 44.2mpg that the Fiat 124 Spider managed in our True MPG test isn't just impressive for a convertible sports car, but also slightly more than its official average.

You also get peppy performance and a supple ride, but will have to scour the classifieds if you want a 124 Spider, because it has been discontinued due to slow sales.

True MPG: 45.1mpg

The MX-5 is closely related to the 124 Spider and actually more fun to drive, but instead of a turbocharged 1.4-litre engine, it uses a naturally aspirated 2.0-litre unit.

In official tests, that makes it slightly less efficient. However, we found it actually averages 3.7mpg more than the Fiat.

True MPG: 50.8mpg

The A5 Coupé is closely related to the A4 saloon that won our overall Car of the Year Award when it first came out, meaning it's comfortable, beautifully built and as quiet as it is efficient.

It's even quite practical by coupé standards.

True MPG: 52.0mpg

In addition to being more fuel efficient than any other coupé we've tested to date in its diesel form, the 4 Series is fun to drive, well equipped and spacious enough for four.

True, it's due to be replaced later this year, but if you're not bothered by that, the good news is it makes big discounts easier to come by.

And what about the least efficient...?

True MPG: 23.5mpg

With a 503bhp twin-turbocharged petrol V6 under its bonnet, the Giulia Quadrifoglio is designed for performance rather than efficiency, and that's reflected in its poor True MPG result.

However, it's our reigning Performance Car of the Year, which tells you just how good it is at the things it specialises in.