True MPG: Most efficient real-world diesel cars
What Car?'s True MPG tests show what fuel economy you can really expect from a car. Here, we reveal the best-performing diesel-powered cars we've ever tested.....
The official government 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.
You won't need to 'hypermile' to achieve these results
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're counting down the 10 most efficient diesel-engined cars we've tested to date. Even though a lot of car buyers are choosing petrol or electrified cars over diesel power these days, the fuel is still a top choice if you regularly drive long distances on the motorway and want to keep your running costs low.
Our top 10 includes family cars, coupés, SUVs and even a people carrier. Read on to find out more about them. And if you're struggling to decide which fuel type is right for you, try our What Fuel tool.
10: Audi A5 2.0 TDI
True MPG 50.8mpg
The A5 is a seriously impressive executive coupé; in fact, it's our Coupé of the Year for 2019.
This 2.0-litre diesel engine is a great choice too, thanks to its punchy performance and good fuel economy, netting you more than 50mpg in real-world conditions.
10: Audi A5 2.0 TDI - interior
Since our tests, this model's name has changed, though, so this is now the 40 TDI.
9: Volkswagen Touran 1.6 TDI 115
True MPG 50.9mpg
Want to move seven people but don't want an SUV? Enter the Volkswagen Touran. It's one of the best MPVs around, despite being one of the older cars in this market.
9: Volkswagen Touran 1.6 TDI 115 - interior
We like the Touran's superb space and practicality, the fact that it's great to drive, and that you can buy one relatively cheaply thanks to impressive discounts and PCP finance deals.
8: Kia Sportage 1.7 CRDi
True MPG 51.4mpg
If you're looking for a less pricey family SUV, the Kia Sportage should definitely be on your list. You generally get a lot for your money – both in terms of space and equipment – and resale values are good too.
8: Kia Sportage 1.7 CRDi - interior
This 114bhp diesel engine has since been replaced by a newer 1.6-litre variant with the same power output and should also prove to be an economical choice.
7: Vauxhall Insignia Grand Sport 1.6
True MPG 51.8mpg
The Insignia Grand Sport is a popular choice among company car drivers, and it's easy to see why:
7: Vauxhall Insignia Grand Sport 1.6
it's well equipped, entry-level versions won't cost you very much to buy and it's competitive on benefit-in-kind payments. This 134bhp 1.6-litre diesel engine is the sweet spot in the range.
6: Nissan Qashqai 1.5 dCi 110
True MPG 51.9mpg
The Qashqai is consistently ranked among the best-selling cars in the UK, and fortunately this diesel-engined version is also among the most frugal, returning almost 52mpg on our tests.
6: Nissan Qashqai 1.5 dCi 110 - interior
In addition, the Qashqai is one of the most comfortable family SUVs on sale, as well as being reasonably spacious.
5: BMW 4 Series 420d
True MPG 52mpg
The second coupé to feature on this list is the elegant 4 Series, which is a chief rival to the Audi A5.
Although there are more powerful engine options available, this 2.0-litre 420d model is our recommended choice for its speed and flexibility.
5: BMW 4 Series 420d - interior
The 4 Series is well equipped and fun to drive, plus there's space for four inside. It's also available as a convertible if you're looking for roof-down thrills.
4: Ford Mondeo 1.5 TDCi
True MPG 53.7mpg
The Mondeo is spacious and good to drive, offering agile handling and a comfortable ride. And because it doesn't wear a premium badge, big discounts are available to tempt buyers.
4: Ford Mondeo 1.5 TDCi - interior
This 1.5-litre diesel engine is our pick of the range if you've got a lot of miles to cover, because it balances performance and fuel economy so well.
3: Renault Kadjar 1.5 dCi 110
True MPG 55.2mpg
The Kadjar is proof that you can buy a family-size SUV that can return more than 55mpg in real-world conditions.
3: Renault Kadjar 1.5 dCi 110 - interior
In fact, this Renault has the honour of being the most frugal family SUV we've ever tested, thanks to its smooth and reasonably punchy 1113bhp 1.5-litre diesel engine.
2: Seat Leon 1.6 TDI 110 Ecomotive
True MPG 56mpg
The Leon is an appealing family hatchback, offering tidy handling, low running costs and plenty of equipment on most trim levels.
2: Seat Leon 1.6 TDI 110 Ecomotive - interior
There's more wind and road noise than you'll find in rivals, but it's an interesting alternative to many of the class leaders, and as our tests have shown, it's also highly efficient.
1: Vauxhall Astra 1.6 CDTi 110 Ecoflex
True MPG 56.3mpg
This Astra is the most efficient diesel-engined car we have ever tested, managing more than 56mpg in real-world conditions and an astonishing 70mpg on country roads.
1: Vauxhall Astra 1.6 CDTi 110 Ecoflex - interior
The latest Astra is also comfortable and spacious and undercuts the rival Volkswagen Golf on price by a big margin once discounts are taken into account.