True MPG: most efficient coupes, convertibles and sports cars 2020
What Car?'s True MPG tests show what fuel economy you can really expect from a car. Here, we reveal the best and worst-performing coupés, convertibles and sports cars we've tested...
The miles per gallon (MPG) figures published in sales brochures can tempt you into buying 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, 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.
The 10 most fuel efficient coupés, convertibles and sports cars cars:
10. BMW M2
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.
8. BMW 4 Series 43oi Convertible
True MPG 34.9mpg
Fractionally more efficient than the Cayman is the BMW 430i Convertible, despite it being a four-seater with a folding metal roof, so considerably heavier.
7. Audi TT Roadster 1.8 TFSI
True MPG 39.8mpg
We've always rated the TT Roadster highly, with this version's near-40mpg average fuel economy joining a list of attributes that also includes sharp handling and a gorgeous, high-tech interior.
6. Audi TT Coupé 1.8 TFSI
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.
5. Mini Convertible Cooper
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.
4. Fiat 124 Spider 1.4 140
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.
3. Mazda MX-5 2.0
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.
2. Audi A5 Coupé 2.0 TDI 190
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.
1. BMW 420d Coupé
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 the least fuel efficient coupé, convertible or sports car...
Alfa Romeo Giulia Quadrifoglio
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.
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