Real MPG: most economical diesel cars - and the least

Real MPG Average 57.9mpg | Town 50.5mpg | Motorway 52.1mpg | Rural 72.6mpg

As if the Skoda Octavia, the thoroughly sensible and highly regarded family car, needed another string to its bow, it takes the crown as the most fuel-efficient diesel car we've ever tested. This is on top of it having terrifically spacious rear seats and a simply enormous boot, as well as interior quality that wouldn't be out of place in a much more expensive car. The 115bhp 2.0-litre diesel engine has plenty of low-down shove, too, which helps to make it relaxing to drive.

In pretty much every economy test, the Octavia impressed, but it was the mighty 72.6mpg figure on rural roads that really stood out. With the exception of the rural figure the Vauxhall Astra (below) achieved, no diesel car on our list recorded more miles per gallon.

Read our full Skoda Octavia review

Real MPG Average 56.3mpg | Town 46.4mpg | Motorway 50.7mpg | Rural 73.7mpg

This model from the previous-generation Vauxhall Astra range is the second most efficient diesel-engined car we have ever tested, managing more than 56mpg in real-world conditions and an astonishing 73.7mpg on country roads. When it was new, the Astra impressed with plenty of interior space, a good amount of standard equipment and attractively low prices. And having been replaced with an all-new model, the 2015-2021 Astra represents terrific value as a used-car buy.

Read our full used Vauxhall Astra (2015-2021) review

Real MPG Average 56.0mpg | Town 46.3mpg | Motorway 50.9mpg | Rural 71.7mpg

The previous-generation Seat Leon might have discontinued several years ago, but it remains an appealing family hatchback. It's better to drive than the marginally more efficient Astra, but still offers plenty of standard equipment. 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. The Ecomotive version that performed so well in our tests received a raft of tweaks to save fuel, but you can expect similar economy from other models in the range. 

Read our full used Seat Leon (2013-2020) review

Real MPG Average 55.2mpg | Town 50.0mpg | Motorway 48.8mpg | Rural 69.1mpg

The Renault Kadjar is proof that you can buy a family-sized SUV that can return stellar real-world fuel economy; in this case, more than 55mpg which makes it the most frugal family SUV we've ever tested. We like the smooth diesel engine, which is reasonably punchy despite a relatively small 113bhp power output. We also like it's spacious inside, and that its boot is larger than the more well-known Nissan Qashqai which it shares its underpinnings with. 

Read our full used Renault Kadjar review

Real MPG Average 54.8mpg | Town 45.8mpg | Motorway 49.5mpg | Rural 70.4mpg

What's not to like about the Skoda 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. 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

Real MPG Average 53.7mpg | Town 47.7mpg | Motorway 47.0mpg | Rural 66.2mpg

After three decades, the venerable Ford Mondeo has now been discontinued – but a good used example is well worth seeking out. Not only is it spacious and good to drive, blending agile handling and a comfortable ride, it was named most reliable executive car in our most recent reliability survey. While our reviewers prefer the larger 2.0-litre TDCI diesel, it's the smaller 1.5-litre engine that is the real-world economy champion.

Read our full used Ford Mondeo (2014-2022) review

Real MPG Average 53.3mpg | Town 46.4mpg | Motorway 47.8mpg | Rural 67.2mpg

Like the Ford Mondeo, the Vauxhall Insignia is no longer sold new, but it makes an interesting alternative executive car choice and costs a lot less than an Audi A4 or BMW 3 Series of similar age. A 1.5-litre diesel engine sounds a little small for a car of this size, but it's far from out of its depth, as those economy figures suggest. Some rivals are more fun to drive, but the Insignia is a comfortable machine in which to clock up big mileages.

Read our full used Vauxhall Insignia (2017-2022) review

Real MPG Average 52.4mpg | Town 45.2mpg | Motorway 47.0mpg | Rural 66.2mpg

The Ford Focus is a household name, 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 on any kind of journey. The Focus remains one of the best-handling family hatchbacks, especially in more sporty ST-Line guise. But regardless of trim, it's well equipped and has spacious rear seats. It's a shame, then, that the boot is on the small side.

Read our full Ford Focus review

Real MPG Average 52.2mpg | Town 45.6mpg | Motorway 46.2mpg | Rural 67.0mpg

Not only does the Audi A4 35 TDI have the most economical engine in the A4 range, but it's also our overall pick of the bunch. It has more than enough grunt to whisk you to motorway speeds effortlessly (0-62mph takes 8.2sec), and it's smoother and quieter than the equivalent diesel engine in its Mercedes C-Class rival. The A4 also has the best-built interior in its class, and it beats the BMW 3 Series when it comes to ride comfort.

Read our full Audi A4 review

Real MPG Average 52.0mpg | Town 46.4mpg | Motorway 45.2mpg | Rural 67.7mpg

It has since been replaced by an all-new model, but the previous BMW 4 Series Coupé 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 used BMW 4 Series (2013-2020) review