Diesel cars use 28% more fuel in the real world than their advertised performance statistics, new data has suggested.
According to The Miles Consultancy, the gap between claimed and real economy figures has also grown – by 3%, compared with 2015’s figures.The miles and expense management company came to this conclusion after analysing mileage and fuel data from 21,200 fleet cars, by comparing each car’s official mpg figure with its actual performance between January and September.
Although overall advertised fuel consumption improved from 62mpg in 2015 to 66mpg in 2016, the real-world economy figure only improved to 47.2mpg.
Petrol cars, meanwhile, recorded a 19% shortfall, achieving an average 9mpg less than the advertised mpg figure.
The gap in economy equates to using £1,800-worth more in fuel over the course of an average three-year/60,000-mile contract, TMC said.
“In this sample alone, we are looking at a total annual discrepancy of around £50m in fuel costs,” said Paul Hollick, managing director of TMC. “The question businesses should ask themselves is whether it is still commercially or environmentally sustainable for them to rely on official figures that are 30% adrift when, these days, they can easily build fully accurate, real-world data about their fleet assets into policy and operational decisions.”
Hollick added that drivers could also play their part to improve real-world full economy. “Of all the factors affecting real-world fuel economy, drivers are undoubtedly the largest influence. Our data enables employers to identify the worst performers and target them for training or other methods of improvement.”
The TMC boss welcomed the upcoming introduction of the ‘real-world’ World Harmonised Light Vehicles Testing Procedure emissions testing cycle, due to start in September, but warned that mpg and CO2 figures will still be obtained under artificial conditions, and said fleets should use tools to help capture fuel use.
