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'Misleading' fuel economy figures and new road tax system 'adds more than £1,000 to car running costs'

The new VED road tax system and misleading fuel economy figures are adding more than £1,000 to long-term car running costs of, according to new research from

The consumer motoring website analysed 118,000 Real MPG fuel reports submitted by UK drivers and found that, on average, a car uses 24% more fuel than it should, while the gap between the laboratory figures and those obtained under real world driving conditions is at its widest point ever, with just one in 10 hitting the official mpg.

Honest John’s managing editor Daniel Powell said: “Real MPG has shown that, for the majority of drivers, advertised fuel economy figures are quite simply too good to be true. As a result, many are finding it increasingly difficult to understand how much fuel a car will use or how polluting it will be.

“We welcome the introduction of the new Worldwide Harmonised Light Vehicles Test Procedure (WLTP), but it remains to be seen if this new laboratory-based test will provide the realistic figures that the public have been crying out for – there’s clearly a need for change in the way that MPG is measured, as the real world figures don’t reflect those of laboratories.”

British motorists, HonestJohn said, are using an estimated 2,970 million extra litres of petrol and an additional 2,609 million litres of diesel every year*, which produces 13.8 million tonnes of CO2 that could have been prevented from entering the atmosphere if cars achieved their official economy.

This means that, while average CO2 emissions for cars have been falling on paper, in the real world they have remained largely stable.

“The Government’s new road tax rules coming into force from tomorrow has also increased the squeeze on motorists by adding more than £500 to the long-term running costs of Britain’s most-popular cars.

For example, from April 1, the UK’s best-selling car - the Ford Fiesta 1.0 EcoBoost 100PS petrol - now costs £5173** to fuel and tax over four years, which is £1372 more than its official fuel economy figures suggest,” Powell said.

The BMW X5 is the UK’s worst performing car for Real MPG, achieving 66.9% of its advertised fuel economy, followed by the Land Rover Discovery Sport and Audi A4 with a respective 67.5 and 68.3%.

The Volvo XC90 (68.5%) and Fiat 500X (69.6%) complete the list of bottom five cars on sale right now for real world economy.

Real MPG was launched in 2011 after received thousands of complaints from readers that their cars could not match the ‘official’ EC fuel economy figures.

Published at, Real MPG invites motorists to submit how many miles their cars actually do to the gallon, covering all major makes and models.

“One of the reasons new cars have performed increasingly poorly is because, since 2015, car manufacturers have been fined by the EC if the corporate average CO2 emissions of their cars exceeds 130g/km according to mpg and CO2 laboratory tests. To avoid the fines, vehicles are increasingly optimised for the laboratory test at the expense of reality.”

From September 2017, the NEDC (New European Driving Cycle) test for new cars will be replaced with the Worldwide Harmonised Light Vehicles Test Procedure (WLTP). However, while the WLTP should be more reflective of real world driving conditions, it will still be laboratory-based.

* Based on Real MPG data and HMRC fuel consumption figures.

** Based on an average price of petrol at £1.17 over four years/40,000 miles.

The worst cars on sale in terms of disparity between claimed and Real MPG fuel economy 

1) BMW X5 66.90%
2) Land Rover Discovery Sport 67.50%
3) Audi A4 68.30%
4) Volvo XC90 68.50%
5) Fiat 500X 69.60%
6) MINI Hatch 70.00%
7) Peugeot 308 SW 70.2%
8) Range Rover Evoque 70.40%
9) Ford Fiesta 71.00%
10) Hyundai Tucson 71.30%


The best cars on sale in terms of disparity between claimed and Real MPG fuel economy 

1) Mazda MX-5 101.50%
2) Toyota Verso 99.50%
3) Toyota GT86 98.40%
4) Subaru Forester 97.10%
5) Peugeot Partner Tepee 92.90%
6) Suzuki SX4 S-Cross 92.0%
7) SEAT Mii 90.6%
8) Volkswagen Jetta 90.40%
9) Suzuki Swift 90.10%
10) Volkswagen Scirocco 88.60%


> VED rules from April 2017

> Independent real world mpg figures and CO2 calculator


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  • Neil - 31/03/2017 14:03

    I have my suspicions that the tax changes are partly influenced by the introduction of WLTP. During the phase-in period we will have old models with official CO2 emissions derived from NEDC, and new models with official CO2 emissions derived from WLTP on sale at the same time. Given that a newer model will probably have lower consumption/emissions than an older one, but consumption/emissions on WLTP will be higher than those on NEDC, there was a possibility that a newer, more efficient car would fall into a higher tax bracket than the older less efficient one. By simplifying the tax system, this situation has been avoided.