True MPG: most efficient diesel cars

They may not be very fashionable right now, but if you do big miles and are looking to keep your fuel costs down, diesel cars still make a huge amount of sense. Here we reveal the most frugal...

Nissan Qashqai True MPG with Nissan logo

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.

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. And because it's not fashionable, big discounts are generally available.

Our top 10 includes family carscoupés, SUVs and even a load-lugging estate car. Read on to find out more about them.

10. Kia Sportage 1.7 CRDi

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Kia Sportage

True MPG 51.4mpg

If you're looking for a frugal family SUV, the Kia Sportage should definitely be on your list. You get a lot for your money – both in terms of space and equipment – and there are plenty of examples of this 114bhp diesel on the used market. It's since been replaced by a newer 1.6-litre variant with the same power output that should also prove to be an economical choice.

Read our full Kia Sportage review >>

9. Vauxhall Insignia Grand Sport 1.6

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New Vauxhall Insignia Grand Sport vs used Audi A4: which is best?

True MPG 51.8mpg

The Insignia Grand Sport is a popular choice among company car drivers, and it's easy to see why: 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.

Read our full Vauxhall Insignia review >>

8. Nissan Qashqai 1.5 dCi 110

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Used Nissan Qashqai

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. In addition, the Qashqai is one of the most comfortable family SUVs on sale, as well as being reasonably spacious.

Read our full Nissan Qashqai review >>

7. BMW 4 Series 420d 

5: BMW 4 Series 420d

True MPG 52.0mpg

It was recently replaced by an all-new model, but the old 4 Series is still an elegant and efficient choice. Although there were more powerful engine options, this 2.0-litre 420d model strikes the best balance between performance and costs. 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.

Read our full used BMW 4 Series review >>

6. Ford Focus 1.5 TDCI 120

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Ford Focus 1.0 Ecoboost 125 Zetec Nav

True MPG 52.4mpg

The Focus is a staple family hatchback choice for many, but there's more reason to choose the big-selling Ford than just popularity. If you go for the 1.5-litre diesel engine on offer, not only will you have plenty of pulling power at your disposal, but it's also a very economical choice. The Focus remains one of the best-handling family hatchbacks, too.

Read our full Ford Focus review >>

5. Ford Mondeo 1.5 TDCi

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Ford Mondeo hatchback front

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. This 1.5-litre diesel engine used to be our pick of the range because of its balance of performance and economy, but it's since been replaced by a duo of 2.0-litre diesels which we haven't economy tested yet.

Read our full Ford Mondeo review >>

4. Skoda Superb Estate 2.0 TDI 150

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Skoda Superb Estate 2019 front right cornering

True MPG 54.8mpg

What's not to like about the Superb Estate? Not only is it massive inside, so it can take all of your passengers, plus their luggage, and still come asking for more, but it's also comfortable and good to drive, too. And if you opt for this 2.0-litre diesel engine, it will even be ruthlessly economical, so you won't spend much time (or money) filling up. It's a no-lose situation if ever we saw one.

Read our full Skoda Superb Estate review >>

3. Renault Kadjar 1.5 dCi 110

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Renault Kadjar front

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. 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.

Read our full Renault Kadjar review >>

2. Seat Leon 1.6 TDI 110 Ecomotive

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2: Seat Leon 1.6 TDI 110 Ecomotive

True MPG 56.0mpg

The previous Leon remains an appealing family hatchback, offering tidy handling, low running costs and plenty of equipment on most trim levels. There's more wind and road noise than you'll find in some rivals, but it's an interesting alternative to many of the class leaders, and as our tests have shown, it's highly efficient.

Read our full used Seat Leon review >>

1. Vauxhall Astra 1.6 CDTi 110 Ecoflex

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Vauxhall Astra front three quarters

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. 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.

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