Consumer magazine What Car has been finding out real-world fuel economy figures as part of its ‘True MPG initiative’ – and the results may surprise you.
The best performer on test was the Seat Leon five-door when blessed with the SE Ecomotive 1.6TDI 110 diesel. It managed 63.2mpg, which was 26.2 per cent lower than its official combined miles per gallon figure of 85.6.
Citroen’s DS3 e-HDi Airdream DSport Plus 1.6-litre diesel came in second place, scoring 63mpg instead of the claimed 74.4mpg – a difference of 15.3 per cent. The Mini Cooper D, meanwhile, was 22.4 per cent off BMW’s 80.7mpg claim, at 62.6mpg.
The worst performer in the top 10 was the Hyundai i20 SE CRDi and its 1.4 diesel, which could muster up 59.4mpg, a mere 13.80 per cent difference compared with the EU-sanctioned 68.9mpg.
Of all the cars in the top 10, the biggest discrepancy between claimed and real-world went to the seventh place Peugeot 308 Allure BlueHDI 1.6-litre diesel. It managed 60.8mpg instead of 88.3mpg, a difference of 31.1 per cent.
Just below that was the Skoda Octavia Greenline III TDi CR 1.6-litre diesel, which was 29.9 per cent too generous with its claimed figure of 88.3mpg compared with the 61.9mpg reality.
Although the Seat came out on top over the last 12 months, the Citroen C3 VTR+ eHDi is still the most fuel efficient car tested since True MPG began in 2012, scoring 70.3mpg.
On the flip side, the True MPG test looked at the very thirstiest engines around. It is no surprise the 6.3-litre supercharged V8 in the Vauxhall VXR8 GTS scored a woeful 19.5mpg, making it the least fuel efficient on test.
Next up was the Porsche Cayenne V8 Turbo and its 20.7mpg, 17.9 per cent lower than the official figure of 25.2mpg.
Third place goes to the 430bhp Aston Martin V8 Vantage S, which drinks a planet-draining 23.2mpg. That figure is, however, 5.9 per cent over the official figure of 21.9mpg. The VXR8 GTS also bettered its official figure by 5.4 per cent.
The car that boasted the biggest difference between what’s on paper and what you get when driving was the Ford Fiesta Zetec S. Its actual figure of 62.8mpg was a hefty 36.8 per cent lower than 39.7mpg it achieved.
What Car editor Jim Holder said: “Buyers get frustrated when they can’t achieve claimed fuel economy figures. That’s because the official EU tests are carried out in a laboratory under very specific conditions that don’t reflect real-world driving.
“However, we took action a few years ago by launching True MPG and have published real-world figures for hundreds of popular vehicles since.”
268 vehicles were tested in normal driving conditions between March 2014 to February 2015. The test includes motorway and A- and B-road driving in towns and villages.
A survey by Emissions Analytics found that smaller cars were not necessarily better on fuel.