True MPG: 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?...
So, you've seen the most efficient cars, all of which average more than 54mpg in real-world driving conditions, but which cars use the most fuel?
Here we answer that question and see just what they do deliver 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 least fuel-efficient cars tested:
10. BMW 3 Series M340i Touring
True MPG 28.0mpg
If you’re after a practical estate that offers effortless performance, and class-leading handling and composure regardless of conditions, look no further. If you're after efficiency, on the other hand, look elsewhere.
9. Audi Q7 50 TDI
True MPG 27.2mpg
Add up all of the stars in our 16-point road test, and the Q7 has one of the highest scores of any car on sale today. The only significant chink in its armour – at least when it comes to this 50 TDI version – is fuel economy.
True MPG 27.1mpg
We're big fans of this family SUV; it was even our 2018 Car of the Year. However, while this turbocharged 2.0-litre petrol version is nice to drive, a True MPG of 27.1 makes it significantly harder to recommend.
7. Mercedes S500
True MPG 26.9mpg
The S-Class has long been one of the best luxury saloon around and is extremely relaxing to drive or be driven in. However, despite featuring mild hybrid technology, the previous-generation S500 version is anything but frugal.
6. Land Rover Discovery 3.0 SDV6
True MPG 26.3mpg
Large, luxurious SUVs aren't an efficient breed, but even by the standards of the class the Land Rover Discovery gulps down a lot of fuel, barely topping 26mpg.
=4. Mercedes-AMG GLC 43
True MPG 25.3mpg
If you get your thrills from blasting away from traffic lights and listening to a piercing V6 soundtrack, the GLC 43 is well worth a look. It’s even practical and easy to drive when you’re in family mode. But it's never what you'd call frugal.
=4. Porsche Macan Turbo Performance Pack
True MPG 25.3mpg
The Macan Turbo is a rival for the GLC 43, and averaged the same 25.3mpg when we put it through our True MPG test. However, it's since been given a new engine and is the more rewarding car to drive.
3. Mercedes S500 Cabriolet
True MPG 25.2mpg
Until it was discontinued in 2020, the S-Class Cabriolet was the best luxury drop-top you could buy. However, it was only for those with a big balance, due to its high price and running costs.
2. Audi SQ5
True MPG 24.6mpg
Like the rival GLC 43 and Macan Turbo, the SQ5 is as heavy on fuel as it is light on its feet – or at least it was until Audi swapped the petrol engine for a diesel. Strengths also include a beautifully built interior.
1. Alfa Romeo Giulia Quadrifoglio
True MPG 23.5mpg
Like so many cars in this bottom 10, the Giulia Quadrifoglio is designed for performance rather than efficiency. Indeed, it's a former What Car? Performance Car of the Year, which tells you just how good it is at the things it specialises in.
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