Currently reading: Four-cylinder Porsche Cayman S has worse real-world fuel economy than Jaguar F-Type
The four-cylinder Porsche Cayman S has fared worse than a V6-powered Jaguar F-Type in new real-world fuel economy testing by Autocar's sister brand What Car?

The Porsche 718 Cayman S has returned poorer real-world fuel economy than the V6-powered Jaguar F-Type in What Car? True MPG testing. 

The findings of the True MPG testing showed that despite Porsche opting to downsize the Cayman S from a six-cylinder to a turbocharged four-cylinder for better efficiency, the model still consumed more fuel than a Jaguar F-Type V6 auto.

See all of the latest What Car?'s True MPG results here

Under True MPG testing, the 718 Cayman S returned 28.39mpg, versus an official figure of 34.9mpg, equating to a shortfall of 18.7%.

The F-Type performed marginally better in the True MPG tests, delivering 28.79mpg, a 14.3% difference over its claimed figure of 33.6mpg.

The Cayman S was one of a batch of 20 models tested under What Car’s new True MPG process. A Porsche spokesman said “the basis of any official Europe-wide Government legislated testing is the NEDC - an agreed industry standard that provides a repeatable consistent platform for cars of all types to be assessed and which intends that data is easily and accurately compared with other cars. The car industry is currently working with legislators on revising the NEDC.

“Of course, the real world will present variations based on road conditions and driving styles. It can be higher than the official standard fuel consumption, but also lower if the driver adopts an appropriate driving style.”

The Porsche spokesman also highlighted the greater efficiency, power and torque in the new Cayman versus its six-cylinder-powered predecessor, as well as the model’s low real-world NOx emissions, under independent analysis.

The top performer in the first batch of True MPG testing was the six-cylinder BMW M2. The BMW strayed from a claimed 33.2mpg by just 5.3%, achieving 31.43mpg.

Meanwhile, other models that underperformed include the Volvo S90 D4. It has an official combined claimed figure of 64.2mpg, but under True MPG testing it achieved only 39.9mpg; this is the largest shortfall of all 20 cars tested, at 37.8%.

Volvo issued the following statement in response to the results: “Volvo cars meet all current emissions standards and figures quoted come from the current European testing procedure.

"There are well-known differences between results from the official laboratory tests and those performed on the roads with results varying due to a number of reasons including driving style, traffic levels and environmental conditions.”

Volvo also stated that the introduction of Real Driving Emissions (RDE) testing from next year will address the differences highlighted by the True MPG testing.

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The Audi A4 3.0 TDI 218 was the next worst performing car, with a 36.2% shortfall on its official fuel economy of 65.9mpg; it returned 42.0mpg. Audi responded to the result, saying: "All new Audi models are tested independently in accordance with the current official Europe-wide government legislated NEDC regime to which every automotive manufacturer must adhere.

"These figures are intended by the NEDC as a guide only and the ‘real-world’ results will, of course, differ depending on a number of factors. This is made clear in all our public-facing communications."

True MPG tests are carried out at Millbrook Proving Ground, which is an approved NEDC testing centre. Conditions for testing are strictly monitored and are completely repeatable, meaning every car is tested under the same conditions. 

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TS7 4 August 2016

Whenever possible...

...I look up the American EPA figures for cars. Mechanically they are identical, where models lare available both sides of the pond. The results, once factored for the smaller USG, are very similar to the real world figures obtained in What Car? et al. The difference being the test cycles used by the EPA are probably closer between cars than an average of owners taken here. Figures for the Cayman aren't avaiable (yet), but for the open versions of both cars they find the Boxter S with a combined mpg of 26, the Jag 25, and the old 6 cylinder Cayman S on 26 - the 6 cyl S performing better in highway conditions than the new 'efficient' one. EPA tests include City, Highway, High Speed, Air Conditioning, and Cold cycles. Acceleration and speeds are far more realistic than the eu ones.
shortbread 4 August 2016

JLR must continue to be honest with their CO2/mpg figures

Watching zze zernamzz win the paper figure wars must be disheartening. But I think JLR should stick to their guns and be as honest as they can with their emission and mileage figures. This will help their reputation in the long term!
legless 4 August 2016

Had an eye opening experience recently

My father and I recently travelled the same 160 mile journey over mixed roads in convoy.

He was driving his 2003 Jaguar XK8 4.2, with the ZF 6-speed auto, and I was driving my 2016 Audi S3 Saloon DSG.

Both cars had a 6-speed automatic gearbox, both develop around 300bhp and both were being driven at near-identical speeds.

Over the whole journey, the fuel economy was 0.7mpg in the S3's favour (32.1mpg vs 31.4mpg in the Jag). Nowhere near as much as you'd expect.

Ski Kid 4 August 2016

agree legless

I had an XJ 3.2 v8 in 1997 when it was launched, a mistake should have got the 4 litre at the time as that was just as economical.I averaged 26 to 28mpg and on a run to RAF Mildenhall airshow got 32mpg without hanging around.A friend has the rs3 and prior to that he had the s3 and the rs3 gets 5 to 6 mpg less than s3.So there you have it a 1997 v8 as economical as the state of art fiddled, fraudulent VW Audi modern offerings.