When it comes to buying a car – new or used – one of the most important factors for many drivers is how quickly it will empty its fuel tank.
With many motorists looking to reduce their costs as much as possible, particularly during this period of financial hardship brought on by the Covid-19 pandemic, the importance of having a frugal motor could be greater now than ever before.
While consumers can get an idea of how economical a car is by the ‘official’ mpg figures published by manufacturers, most buyers know that these claims need to be taken with a pinch of salt.
However, there is one real-world test carried out in the UK that gives a more accurate measurement of how economical cars are on the road.
We’ve listed the top most and least efficient models, which includes diesels, to have been put through What Car?’s True MPG assessment.
MOST EFFICIENT CARS
10. Seat Ibiza 1.0 TSI 95 petrol (from £17,675)
The Seat Ibiza would likely already be on your shopping list if you’re on the hunt for a competent supermini with plenty of space. Its 3-cylinder motor is super frugal
The Seat Ibiza is a great option if you’re looking for a spacious supermini. A strong engine line up, solid build quality and sporty looks, it ticks many boxes for buyers in this segment.
The 1.0-litre three-cylinder petrol engine is also affordable to run. A less potent 80PS version is available in the UK, but it’s the 95PS version What Car?’s test team has judged. Returning 54mpg, it’s over 6mpg short of the claims but still impressively economical.
9. Skoda Superb Estate 2.0 TDI diesel (from £27,960)
The Skoda Superb Estate is proof that large cars can be economical too
If you thought this list would be full of small, efficient cars, you’d be wrong. The Skoda Superb proves big models can be frugal.
A combination of a fuel-supping 2.0-litre diesel engine and the improved aerodynamic efficiency of a longer estate body combines to provide an impressive 54.8mpg – which is less than 3mpg shy of the claims.
=6. Renault Kadjar 1.5 dCi 110 diesel (from £26,495*)
The Renault Kadjar has recently been proved a reliable second-hand motor. Its diesel engine is also fuel efficient, according to What Car?
Renault’s Kadjar recently topped our poll of the most reliable used SUVs, using data from warranty provider Warrantywise. And as well as being dependable, it’s pretty economical too.
The dCi 110 diesel engine is no longer available in showrooms, with Renault pulling all oil burners for the Kadjar in recent weeks. If it’s anything like its counterpart, it should be exceptionally frugal for a mid-size SUV.
=6. Skoda Citigo 1.0 60 petrol (from £8,885**)
Skoda’s Citigo is designed to be an easy-to-drive and affordable town runaround. The least powerful engine in its range returns over 55mpg in real-world tests
The Citigo is Skoda’s answer to a fun, affordable and practical city car. It comes with a range of 1.0-litre three-cylinder petrol engines, with the 60PS tested here being the lowest of the outputs.
Returning over 55mpg in real-world assessments, it will be a cheap runaround for town drivers, though not quite as economical as the official measurements suggest.
= 6. Suzuki Baleno 1.0 petrol (from £12,999**)
The Baleno is an often-overlooked family hatchback, but with the 1.0-litre petrol engine under the bonnet is one of the most efficient
Most buyers in the mid-size hatchback segment will be looking at popular cars like the Ford Focus, VW Golf or Vauxhall Astra. However, there is an offering from Suzuki, which is often overlooked.
The Baleno might not have the premium feel of the Volkswagen or driving characteristics of the Ford, but it does have an efficient 1.0-litre petrol engine. It’s 12 per cent less economical than official measurements suggest, though.
How What Car? tests True MPG
Consumer title What Car? carries out its True MPG test on all new models it assesses.
It says the test is repeatable within one per cent and more realistic than official government fuel economy figures achieved in labs that car manufacturers are obliged to quote.
This is mainly down to the driving technique during the measurements, which is described as ‘gentle’ and ‘within speed limits’, but unlike the official test includes relatively quick acceleration.
‘The True MPG tests are carried out under tightly controlled conditions: climate control is always set to 21 degrees and cars due to be tested are stored overnight at a set 23 degrees so they all start with exactly the same engine temperature and in the same ambient air temperature,’ What Car? states in its explanation of the results.
That means these are figures you can not only expect to achieve, but also have faith in.
The stats don’t include electric cars – for obvious reasons – but What? Car does have a ‘Real Range’ test for zero-emissions models too, informing buyers about the plug-in vehicles that can cover the longest distances between charges.
You can also find out which electric vehicles have the longest claimed ranges.
5. Volkswagen Up 1.0 75 petrol (from £12,440*)
The Up is the sister car to the Skoda Citigo. With VW’s more potent 75PS 1.0-litre motor, it return almost 60mph
Despite fuel economy being down almost a fifth on the official claims, the VW Up with the 75PS 1.0-litre engine is still one of the most frugal models What Car? has put through the True MPG tests.
Returning just shy of 60mpg, it means this is an economical city car as well as one oozing style, desirability and plenty of character.
4. Seat Leon 1.6 TDI 110 Ecomotive diesel (from £19,595**)
A new Leon has replaced this model this summer. With the 1.6-litre diesel Ecomotive engine under the bonnet, it’s one of the most frugal family cars
There’s an all-new Seat Leon in showrooms from this summer, which is based on the latest mk8 VW Golf.
The version What Car? has tested is the previous generation Leon, which can be found as part of dealers’ clearance stock, but most likely on the used market. If you can track down a brand new model with a big discount, it will be a brilliant bargain family car.
3. Vauxhall Astra 1.6 CDTi 110 Ecoflex diesel (price from £20,090*)
The Ecoflex engine has since been replaced with a rebranded Ecotec unit. It should still perform around the same as the model tested here by What Car?
The Ecoflex engine has since been replaced by a 1.6 CDTi Ecotec motor, though it promises to return similar levels of efficiency. And over 85mpg is a seriously big claim.
Unfortunately, What Car?’s test revealed that, in reality, owners won’t get near that bloated stat. However, it does return over 56mpg, which makes it one of the most economical models the consumer title has reviewed yet.
2. Suzuki Celerio 1.0 petrol (price from £8,999**)
The Celerio was, for a time, one of the cheapest new cars you could buy in Britain. You might struggle to find zero-mile examples in Suzuki showrooms today
The Celerio is a cheap car, priced from less than £7,000. It’s not what you’d call luxurious, but the peppy 1.0-litre engine combined with a lightweight and compact body means it’s slower to slurp petrol than almost any other model on sale.
The 57.8mpg figure achieved by What Car? is very close to what the official test suggests you’ll get, too.
1. Suzuki Ignis SHVS mild hybrid petrol (from £16,749)
Topping What Car?’s test is the Suzuki Ignis SUV with a mild-hybrid powertrain. It returned almost 60mpg in the auto magazine’s assessment
The SHVS version of the Ignis, which is front rather than four-wheel drive, is the most efficient car What Car? has tested. It’s what’s called a ‘mild hybrid’. That means it has a small electric motor to supplement the 1.2-litre petrol engine under the bonnet.
The compact crossover achieves almost 60mpg in the True MPG test. And even if you wanted a model with the extra security of four-wheel drive, the figure drops to just 53.3mpg.
Least fuel efficient cars tested by What Car?
The 3 Series Touring might be practical, but in the powerful M340i guise is pretty thirsty
10. BMW 3 Series M340i Touring petrol (from £52,375)
This sporty BMW 3 Series is 20 per cent less economical than claimed, returning just 28mpg.
9. Audi Q7 50 TDI diesel (from £57,965)
Heavy SUVs are not likely to be frugal, and the Q7 is a prime example of that, even when powered by a diesel engine.
8. Volvo XC40 T4 petrol (from £32,770*)
Volvo is ditching conventional internal combustion engines, focusing on hybrid and electric powertrains. This petrol T4 is no longer on sale.
7. Mercedes S500 petrol (from £76,640*)
The S-Class equipped with the six-cylinder petrol engine is unsurprisingly uneconomical. A new S-Class has been confirmed for next year.
6. Land Rover Discovery 3.0 SDV6 diesel (from £57,720*)
Another large SUV to feature in the list is the Land Rover Discovery with the since-replaced 3.0-litre SDV6 diesel powerplant.
The AMG GLC 43 ticks all the boxes for an inefficient model – it’s large, heavy and powered by a thunderous engine
=4. Mercedes-AMG GLC 43 petrol (from £54,420)
The AMG GLC 43 ticks all the relevant boxes for a non-efficient vehicle – it’s large, heavy and has a potent petrol engine under driving all four wheels.
=4. Porsche Macan Turbo Performance Pack petrol (from 68,910)
The potent Porsche Macan Turbo is the first model in this list to have an True MPG figure that betters its official claim. However, it’s still one of the biggest fuel guzzlers What Car? has tested.
3. Mercedes-Benz S500 Cabriolet petrol (from £125,010*)
The S500 is no longer on sale in the UK. But there is still a range of expensive drop-top S-Class models, all with thirsty petrol powerplants.
2. Audi SQ5 diesel (from £55,745)
Audi’s decision to fit its powerful SQ5 with a diesel engine instead of petrol power would have partly been to ensure the fuel economy is practical. Still, less than 25mpg is lower than you’d expect.
1. Alfa Romeo Giulia Quadrifoglio (from £67,195)
Surprisingly, it’s a family saloon that props up the bottom of the What Car? True MPG league table. This is no ordinary saloon, though. It’s the super-fast Alfa Giulia Quadrifoglio.
The Alfa Romeo Giulia Quadrifoglio is the least efficient model What Car? has tested
*engine is no longer on sale. Price provided is for replacement engine versions in showrooms today
**model no longer on sale. Price based on RRP when last available
Some links in this article may be affiliate links. If you click on them we may earn a small commission. That helps us fund This Is Money, and keep it free to use. We do not write articles to promote products. We do not allow any commercial relationship to affect our editorial independence.