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New cars 5.4pc less efficient than official figures suggest

New petrol, diesel and hybrid cars are on average almost 5.5 per cent less efficient than their official fuel consumption figures suggest, according to new research by Britain’s leading new car buying platform, What Car?. The vast majority of car models are similar here.

What Car? tested 56 new petrol, diesel and hybrid models that have been type approved under the new, tougher, Worldwide Harmonised Light Vehicle Test Procedure (WLTP) emissions and fuel economy tests. The vehicles tested ranged from small hatchbacks to large SUVs and each model was subjected to What Car?’s independent True MPG test to determine its real-world fuel economy.

On average, new petrol, diesel and hybrid vehicles are 5.4 per cent less efficient than the WLTP figures that manufacturers have to quote, but the research revealed significant differences between models. The worst performers were found to be more than 20 per cent less efficient than their official figures, while the best performers were found to be 15 per cent more efficient.

The tougher and longer WLTP emissions and type approval test was introduced in 2017 by the European Commission and became mandatory for all new vehicles from September 2018 onwards. The WLTP test replaced the previous New European Driving Cycle (NEDC) type approval test, which dated back to the 1980s*, with the aim of providing more accurate fuel consumption figures for new car buyers.

The new WLTP test is a significant improvement over the NEDC test, according to What Car?’s figures. A sample of 159 vehicles tested under the NEDC protocol showed an average discrepancy of 20.2 per cent between True MPG and the manufacturer quoted figures, with the worst performers as much as 40 per cent less efficient than advertised.

Steve Huntingford, editor of What Car?, said: “For years, most buyers have taken the official fuel economy figures with a grain of salt. Our research shows that while the latest test is more accurate, there are still large differences on some makes and models, which is why it’s important for buyers to do their research before buying.

“Our free True MPG tool is unique to the industry and helps give new car buyers an accurate representation of their vehicle’s real-world fuel consumption.”

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What Car?’s True MPG tests show what fuel economy drivers can really expect from a car, whether it’s a family hatch, an SUV or even a sports car. The tests are conducted on a rolling road in strictly controlled laboratory conditions to ensure they’re comparable, but they’re based on a real route that includes a mix of town, rural and motorway driving. To find out more, visit