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Real MPG: most efficient coupes, convertibles and sports cars
What Car?'s Real 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...
Buying a coupé, convertible or sports car doesn't mean you need to spend a lot more at petrol stations, because in a lot of cases, they're actually quite efficient.
That's because some models are offered with a wide range of engines, including efficient diesels and larger (and often thirstier) petrols. Mind you, not every coupé, convertible or sports car offers such choice, but some are simply smaller and lighter, and therefore surprisingly economical.
So, which are the most efficient you can buy? Here, we reveal the 10 most efficient coupés, convertibles and sports cars that have been put through our Real MPG tests. At the other end of the scale, we'll also show you the three that used the most fuel.
1. The most fuel efficient coupé, convertible or sports car: BMW 420d Coupé
Real MPG 52.0mpg | Town 46.4mpg | Motorway 45.2mpg | Rural 67.7mpg
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. The version we tested for efficiency has now been replaced by the second-generation BMW 4 Series but if you're not bothered by that it makes a brilliant used buy.
Read our full used BMW 4 Series buying guide
How we test for a car's Real MPG
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, our Real 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. We also weigh each car, check the tyre pressures, set the climate control to 21C (or the midway point if it has manual air conditioning, with the fan speed on its lowest setting) and turn off any electronics to limit any interference with our tests.
To make our tests even more accurate, we fit an exhaust connection to measure the emissions and sample them every second. We then calculate the overall Real MPG score with the average of those readings.
Read more: How we test a car's real fuel economy
The best of the rest: coupés, convertibles and sports cars
2. Audi A5 Coupé 2.0 TDI 190
Real MPG 50.8mpg
The A5 Coupé is closely related to the Audi A4 – which was named What Car? Car of the Year when it was first launched. It's comfortable, beautifully built, as quiet as it is efficient, and even quite practical by coupé standards.
Read our full Audi A5 review or see our latest Audi deals
3. Mazda MX-5 2.0
Real MPG 47.9mpg
The MX-5 gets two engine options, a 1.5-litre petrol engine or a larger 2.0-litre unit. In official tests, the 1.5-litre was slightly more efficient, but in our Real MPG tests, the 2.0-litre beat it by 3.9mpg.
Read our full Mazda MX-5 review or see our latest Mazda deals
4. Fiat 124 Spider 1.4 140
Real MPG 44.2mpg
The 124 Spider's result in our Real MPG test isn't just impressive for a convertible sports car but is also slightly better than its official figure. 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.
Read our full used Fiat 124 Spider buying guide
5. Mazda MX-5 1.5
Real MPG 44.0mpg
The MX-5 – which came in third place in 1.8-litre form – is closely related to the 124 Spider but is more fun to drive. We suspect this 1.5-litre version proved less efficient than the 1.8 in our tests because it needs to be worked hard to get the most performance out of it.
6. Mini Convertible 1.5
Real 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 Real MPG figure of 43.4mpg with the 1.5 three-cylinder engine, it still makes plenty of sense.
Read our full Mini Convertible review or see our latest Mini deals
7. BMW 420d Coupé
Real MPG 42.4mpg
One of the great things about the 4 Series is the engines. In this instance, the 2.0-litre turbocharged diesel in the 420d is the most efficient of the bunch, and achieved a decent 42.4mpg during our Real MPG tests. While the 420i is our pick of the range, the 420d makes sense if efficiency is a priority.
Real MPG 40.4mpg
As good as the TT Roadster is, it's the hard-top version that we'd choose, and 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.
Read our full Audi TT review or see our latest Audi deals
9. Audi TT Roadster 1.8 TFSI
Real 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.
Read our full Audi TT Roadster review
10. Volkswagen T-Roc Cabriolet 1.5 150
Real MPG 39.0mpg
Being an SUV, the T-Roc Cabriolet isn't the most conventional convertible. However, it is at least quite efficient, thanks in part to its 148bhp 1.5-litre engine. In other areas, it offers a lofty driving position, a comfortable ride and generous equipment levels.
Read our full VW T-Roc Cabriolet review or see our latest Volkswagen deals
And the least fuel efficient coupés, convertibles and sports cars...
3. Porsche 718 Cayman S 2.5
Real MPG 28.4mpg
Both the 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, and they're not that efficient.
Read our full Porsche 718 Cayman review or see our latest Porsche deals
2. Mercedes S-Class Cabriolet S500
Real MPG 25.2mpg
Mercedes no longer makes the S-Class Convertible and didn't sell a whole lot of them. We suspect there are several reasons for this, with one being the expensive list price, and the other the thirsty V8 and V12 petrol engines. As a used buy they make a lot more sense, but only if you can afford the eye-watering fuel bills.
Real MPG 24.2mpg
It's hardly surprising to see a convertible as the least efficient car on this list, because convertibles tend to be heavier than their coupé counterparts. In this instance, though, the least efficient car is the Lexus LC 500 Convertible. It's powered by a 5.0-litre V8 engine that's a joy to drive and listen to, but it did only manage 24.2mpg during our Real MPG tests.
Read our full Lexus LC Convertible review or see our latest Lexus deals
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