Diesels from 2016 are the worst offenders, according to new data.

Drivers could be burning as much as 75 percent more fuel than their cars’ official consumption figures suggest, according to new data.

Connected car app company Carly has released data for more than one million vehicles worldwide – including 150,000 in the UK – and found a year-on-year growth in discrepancies between official consumption figures and real-world efficiency from 2004 to 2016.

According to Carly, the most significant difference was found in diesel cars from 2016, achieving an average of 75 percent higher consumption rates than stated in information given by the vehicle manufacturer.

Given that the RAC Foundation put the average official economy figure for a diesel vehicle in 2016 was 62.5mpg, Carly has estimated that motorists driving 12,000 miles a year could be spending up to £815 more than expected on fuel alone.

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‘There is an ongoing conflict of interest regarding fuel consumption. Over the years the regulations require less and less CO2 emissions, however, drivers want more powerful and luxurious vehicles,’ said Avid Avini, one of Carly’s founders.

‘With each new C02 reduction strategy, manufacturers have had to reduce fuel consumption, however due to tests being carried out in laboratories rather than the real-world, the data shows consumption to be improving.

‘Miles per gallon is one of the key concerns of UK drivers, and while it can be difficult for manufacturers to predict consumption, as it is very much dependent on individual driving style, a discrepancy of this size is of concern to consumers relying on manufacturer figures.’

The news comes just six months after the European Union introduced a new type of emissions and economy test for new models. Designed to provide a more representative consumption figure, the ‘WLTP’ test replaces the existing lab-based NEDC test. The new form of testing will not become commonplace until August this year, though, and some cars will still use NEDC figures until the start of 2019.

Find out more about the WLTP emissions and economy test.