Which? is calling for more realistic car fuel economy testing after finding 98% of the cars we tested couldn’t match or beat their miles per gallon (mpg) claims.
The cost of fuel is one of the biggest concerns for consumers so the fuel efficiency of new cars has become an important selling point.
We tested 200 new cars across 2013 and 2014 and found that all but three of them fell short of their official mpg figures by 13% on average, resulting in drivers spending £133 more a year on fuel.
The official test used by carmakers is outdated and contains a number of loopholes that lead to unrealistic figures.
Manufacturers are allowed to reduce results by 4% at the end of the test, can opt to only test in a car’s ‘eco’ mode, turn off lights and air-con, and increase tyre pressures above the recommended levels to reduce rolling resistance.
It also doesn’t accurately reflect real-life scenarios, such as motorway driving.
Consumers are being misinformed about their cars’ fuel consumption in advertising and at point of sale, which means they’re likely to end up spending more on fuel.
The car that performed worst compared to its official mpg figure was the Mitsubishi Outlander PHEV (a plug-in hybrid), which overstated its mpg by a staggering 120%, costing £459 a year in unexpected fuel costs.
But the car that hit its owners’ pockets the hardest was the Jeep Grand Cherokee – based on Which? tests, drivers will shell out up to £854 a year more on fuel. Other cars that will cost owners a lot more to fuel are the BMW 4 Series Gran Coupé (£421), BMW X4 (£419) and Volvo V60 Plug-In Hybrid (£352).
An improved test, which closely mirrors the one used by Which?, is due to be introduced from 2017, but the European Commission is facing pressure from the car industry to delay this change until 2020 and any further delay will only end up costing consumers.
Which? is urging the EC to stand firm and implement the new test in 2017 as planned.
Which? executive director Richard Lloyd, said: “The cost of fuel is one of the biggest concerns for consumers which is why fuel efficiency has become an important selling point for new cars.
The new test should be brought in without delay so consumers are no longer misled by fantasy mpg figures.”
Until a more realistic test is introduced, drivers can check the Which?-tested mpg figures for hundreds of cars in our online car reviews.