After the VW crisis, is your car’s miles-per-gallon rating accurate?

Many drivers complain that carmakers’ official claims for miles-per-gallon performance are rarely delivered – and the difference is costing them money

The adverts promise as much as 90 miles per gallon on new super fuel-efficient engines, yet on the road the average is only 50mpg-60mpg. As the emissions scandal engulfs Volkswagen, carmakers face a second onslaught from drivers furious about fuel consumption that is often one-third less than claimed.

VW unveiled its Golf TDI BlueMotion two years ago, claiming “low emissions and incredible fuel economy”. The 2013 TDI model would give drivers 88.3mpg, said VW, in the car packed with fuel-saving measures for “cleaner, greener driving”. But according to the HonestJohn motoring website, where 68,000 drivers of all makes and models have posted their on-the-road fuel consumption figures, this particular model of the Golf has only managed 58.6 mpg on the road, just 66% of the figure claimed by VW.

But it’s not just the beleaguered German manufacturer that makes ambitious claims about fuel consumption. Plenty of other cars return less than 70% of the stated mpg figure, according to the HonestJohn data – and the biggest gap between claim and reality appears to lie with cars promoted as the most fuel-efficient.

The popular 2015 Ford Focus 1.5 TDCi claims to give 74.3mpg, but drivers say they typically manage only 48.3. The 2014 Vauxhall Corsa 1.4 Automatic claims to give 47mpg-60mpg but the reality is closer to 33mpg. Across all cars, average fuel consumption was 86% of the manufacturers’ claims. HonestJohn’s figures are based on drivers who have submitted mpg figures to the website, which means it is not strictly comparable to tests done in laboratories, but does give an indication of the on-the-road experience.

In March consumer group Which? reported that 98% of the 200 cars it tested over the previous two years did not match or beat their mpg claims, with all but three missing their official figures. It claimed motorists typically spend an additional £133 a year on fuel because of the discrepancy.

In Italy, consumer activists have gone further and are taking both VW and Fiat to court over advertised mpg claims. Altroconsumo, Italy’s equivalent of Which?, performed tests on a Volkswagen Golf last year which it says showed fuel consumption levels 50% higher than the figuresofficially declared by VW. It calculated that buyers could be spending as much as €502 (£371) a year more on fuel than expected from the company’s advertisements. A collective action against VW was launched earlier this year and is expected to be put before a court in Venice next month.

But why have manufacturers been free to advertise mpg figures that bear so little resemblance to reality? One angry UK driver, who bought an Audi A3 TDI (part of the VW group) after adverts which said it was “the most fuel-efficient Audi ever”, was so furious that he was getting nowhere near the claimed 68.9mpg that in 2013 he took his case to the Advertising Standards Authority.

VW argued that it had “occasionally” encountered such a complaint before, and put it down to “infinite variations in driving styles and in road, car and weather conditions”. But the ASA said it was guilty of misleading advertising. Since then, carmakers have been a little more circumspect in their claims, and the small print of adverts now tend to say that the quoted mpg figures “may not reflect your actual during experience”.

Official fuel figures published in adverts are obtained from a series of tests known as the New European Driving Cycle, last updated in 1997. They are conducted under laboratory conditions – but power-sapping electrical features which would increase fuel consumption remain switched off during tests. Manufacturers have long been accused of using specially prepared cars to produce the best possible figures. Many years ago the average discrepancy between a car’s official combined fuel economy figure and what a driver could expect was about 8%. But in recent years manufacturers have become more skilled at producing test cars that record low emissions and very high mpg.

Monique Goyens, director general of BEUC, the European Consumer Organisation, says: “We’ve been saying long before the VW scandal broke out that one of the problems in the EU, unlike in the US, is the absence of a surveillance system that would require independent on-the-road testing. The EU needs to implement such a system to restore trust among consumers in emissions and fuel consumption test programmes.

“It is essential the EU starts work on developing a robust on-road vehicle test which could do away with the need for laboratory fuel consumption and CO2 emissions testing. The fact is that EU vehicle emissions and fuel consumption testing has been broken for a long time and consumers are desperate for a better system.”

David Ross, new car editor at, says: “There is a much bigger picture, and that’s the entire way the official fuel consumption tests are carried out. They’ve been in use since the 1970s and are intended to give potential buyers comparative information about the relative fuel consumption of different cars.

“But there is a big caveat here according to the Department for Transport – the figures quoted are obtained under specific test conditions and ‘may not necessarily be achieved under real life’ driving conditions. That’s the problem. The test is outdated and not representative of real-life driving. That’s why so many owners are frustrated about the fuel economy they’re seeing compared with the ‘claimed’ figures. Over the past 10 years, the difference between the official claimed figures and what motorists are actually seeing has increased.”

In June Volkswagen announced the official fuel economy figures for its new Passat BlueMotion saloon and estate car, powered by a 1.6-litre TDI diesel engine. A figure in both cars of “up to 76.3mpg” will be possible, it claimed with CO2 emissions as low as 95g/km.

“These outstanding performance figures make sure drivers will have incredibly low running costs as well as no road tax or congestion charges, making them very appealing to businesses,” it said at the time. Given the furore over VW’s data, those claims are likely to come under intense scrutiny over the next few months.

A spokesman for the Society of Motor Manufacturers and Traders told the Guardian consumers should be reassured that cars sold in the UK must comply with strict European laws: “All must complete a standard emissions test, which unlike in the US is independently witnessed by a government-appointed agency. On the separate ongoing debate about real-world testing, the industry accepts the current test method for cars is out of date and is seeking agreement from the European commission for a new emissions test that embraces new testing technologies and which is more representative of on-road conditions.”

The new test is not scheduled to come into force until 2017; amid the current controversy, that date must surely be brought forward.

A buyer’s tale – VW Scirocco

Alex Jackson bought a VW Scirocco R-Line 2.0 TDI 18, with claimed figures of 64.8mpg. He wrote on the PistonHeads website: “I know from experience that cars never achieve official figures, but I thought it might get close. In reality I’m achieving around 45mpg-46mpg at best. I sold my BMW 330D to buy the Scirocco thinking it would be better on fuel, but in reality I could achieve the same in my Beemer, so I feel I am wasting a lot of money.”


Miles Brignall

The GuardianTramp

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