New petrol, diesel and hybrid cars are, on average, 5.4% less efficient than their official WLTP fuel consumption figures suggest, according to new research by What Car?.

It tested 56 new models under its independent True MPG test, to determine its real-world fuel economy. The figure was then compared to the manufacturer’s claimed figure.

On average, vehicles were 5.4% less efficient than the WLTP figures suggested, but the research revealed significant differences between models.

The worst performers were found to be more than 20% less efficient than their official figures, while the best performers were found to be 15% 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 significantly more accurate than the NEDC test, according to What Car?’s figures. In a previous study of 159 vehicles tested under the NEDC protocol, there was an average discrepancy of 20.2% between True MPG and the manufacturer quoted figures - with the worst performers as much as 40% 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.”

What Car? publishes its True MPG data on its website.

Worst real-world MPG performers:

Make	Model	Engine	Trim	Average True MPG	WLTP Combined	Shortfall
Volvo	XC40	T4	R-Design Pro	27.1	34.8	-22.1%
Volvo	V60	D4	Momentum Pro	40.1	49.5	-19.0%
Renault	Clio	TCe 100	Iconic	44.4	54.3	-18.2%
BMW	3 Series	320d	Sport	47.2	57.6	-18.1%
Volvo	XC40	D4	First Edition	35.4	42.7	-17.1%
BMW	3 Series Touring	M340i	M Sport	28.0	33.6	-16.7%
BMW	1 Series	118i	M Sport	36.3	42.8	-15.2%
Volvo	S60	T5	R-Design Plus	32.5	38.2	-14.9%
Ford	Focus	1.5 Ecoblue 120	ST-Line	52.4	61.4	-14.7%
Kia	Sportage	2.0 CRDi 48V	GT-Line S	35.7	40.9	-12.7%

 

Best real-world MPG performers:

Make	Model	Engine	Trim	Average True MPG	WLTP Combined	Improvement
Honda	CR-V	2.0 i-MMD Hybrid	SR	47.4	40.9	15.9%
Mazda	MX-5	2.0	GT Sport Nav+	45.1	40.9	10.3%
Skoda	Karoq	1.5 TSI	SE L	44.2	40.5	9.1%
Dacia	Logan Stepway	Tce 90	Comfort	47.7	44.3	7.7%
Skoda	Superb Estate	2.0 TDI 150	SE	54.8	51.5	6.4%
Peugeot	Rifter	1.5 Blue HDi	GT Line	50.5	47.9	5.4%
Volkswagen	Polo	1.0 TSI	Beats	51.8	49.6	4.4%
Seat	Ateca	1.5 TSI	FR	44.5	42.8	4.1%
Audi	Q5	40 TDI	S line	39.0	37.7	3.4%
Citroen	Berlingo	Puretech 110	Flair	41.1	39.8	3.3%