The gap between official MPG figures and real-world performance will remain significant despite regulatory change later this year, according to Emissions Analytics.

Incorporating the use of air conditioning, the gap between official mpg figures and real-world EQUA Index Mpg has risen to 29% on average.

Although the World-Harmonised Light-Duty Vehicles Test Procedure (WLTP) will be introduced from 1 September this year to certify the carbon dioxide and fuel economy of cars, Emissions Analytics says it will only halve the current variations between official and real-world fuel economy and not eliminate them altogether.

According to the firm’s EQUA fuel economy data, there was a five percentage point increase in the gap between official and real-world mpg in 2016, reaching 29%. This follows data published this week by UK mileage and expenses management specialist TMC that indicates the gap between diesel cars’ official and real-world fuel economy grew to 28% last year.

Emissions Analytics said the WLTP standard will still be an improvement on the existing type approval process, which incorporates the New European Driving Cycle (NEDC), largely due to the removal or restriction of loopholes in the procedure. However, it added that “the test cycle itself is not much more representative of real-world driving, as it remains in the laboratory with no changes in elevation and still modest acceleration rates”.