WhatCar magazine names and shames best and worst in true MPG lists.

• Seat Leon TDI is most efficient in What Car?’s tests; Vauxhall VXR8 the least
• Aston Martin V8 Vantage S surpasses official MPG figure, Ford Fiesta Zetec S Red Edition was the furthest away
• 268 cars tested during past 12 months

The most fuel-efficient car tested by the What Car? True MPG team over the last 12 months* – topping more than 200 other models – was the Seat Leon 5DR SE Ecomotive 1.6 TDI, managing a real-world average fuel economy figure of 63.2mpg. 

The top three best cars (yet they are still way below claimed)

The Bottom Three - (but aren't they a fun bunch)

Since launching True MPG with official fuel partner Tesco in 2012, almost 500 cars have been assessed in real-world conditions, using cutting-edge test equipment, achieving economy figures that are an average of 20% lower than the Government figures. 

The most efficient vehicles tested over the past 12 months

Make	Model	Derivative	Fuel	Engine size (litre)	Power (PS)	Official Combined MPG	True MPG	Difference
SEAT	Leon 5DR	SE Ecomotive 1.6 TDI 110	Diesel	1.6	110	85.6	63.2	-26.20%
Citroen	DS3	e-HDi Airdream DSport Plus	Diesel	1.6	115	74.4	63	-15.30%
Mini	Cooper	D	Diesel	1.5	114	80.7	62.6	-22.40%
Skoda	Octavia	Greenline III TDi CR	Diesel	1.6	110	88.3	61.9	-29.90%
Honda	Civic	i-DTEC EX+	Diesel	1.6	118	72.4	61.8	-14.60%
SEAT	Leon ST	SE Ecomotive 1.6 TDI 110	Diesel	1.6	110	85.6	61.5	-28.20%
Peugeot	308	Allure BlueHDi	Diesel	1.6	120	88.3	60.8	-31.10%
Citroën	C4 Cactus	Flair BlueHDI	Diesel	1.6	100	83.1	60.1	-27.70%
Skoda	Octavia	Greenline III TDi CR	Diesel	1.6	110	88.3	59.4	-32.70%
Hyundai	i20	SE CRDi	Diesel	1.4	90	68.9	59.4	-13.80%

Vauxhall’s VXR8 was the least efficient overall, recording a paltry 19.5mpg; however, like the Aston Martin, it actually exceeded its official figure of 18.5mpg. 

Least efficient vehicles tested over the past 12 months

Make	Model	Derivative	Fuel	Official Combined MPG	True MPG	Difference
Vauxhall	VXR8	GTS	Petrol	18.5	19.5	5.4%
Porsche	Cayenne	V8 Turbo	Petrol	25.2	20.7	-17.9%
Aston Martin	V8 Vantage S	N430	Petrol	21.9	23.2	5.9%
Porsche	Macan	Turbo S-A	Petrol	30.7	23.4	-23.8%
Lexus	RC-F	F Sport V8	Petrol	26.2	23.8	-9.2%
Audi	S8	SE Executive LWB	Petrol	29.4	24.7	-16.0%
Jaguar	F-Type	R	Petrol	25.5	25.7	0.8%
Mitsubishi	Shogun	DI-DC LWB SG4	Diesel	33.2	26.5	-20.2%
Jaguar	F-Type	V6	Petrol	32.8	26.7	-18.6%
Subaru	WRX STi	Symetrical AWD	Petrol	27.2	26.9	-1.1%

Even the Seat’s table-topping figure was below its claimed figure of 85.6mpg – a result of manufacturers being forced by legislation to test their cars in laboratory conditions. 

The Citroën C3 VTR+ e-HDi Airdream remains the most efficient car, on the road according to True MPG analysis, achieving 70.3mpg. 

Whatcar.com 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.”

The testing has also highlighted an unexpected trend among high-performance cars for getting closest to their official claimed fuel economy figures.

 While far from the most economical overall, the Aston Martin V8 S, which packs 430bhp, beat its official fuel economy figure by 6% – achieving 23.2 instead of 21.9mpg. 

Another powerful V8-powered sports car, the new Jaguar F-Type R, was the only other vehicle to achieve the same feat during the past 12 months, with a True MPG figure of 25.7 compared to its official 25.5mpg.

Alternatively, the Ford Fiesta Zetec S was furthest away from its EU-sanctioned fuel economy, coming in 37% below claimed consumption figures.

Whatcar.com True MPG data is scientifically calculated by experienced engineers, who drive test vehicles over a variety of real roads, including motorway, A- and B-roads and in towns and villages.

Please visit http://www.whatcar.com/truempg/my-true-mpg for more detailed information.