Why do cars not achieve the claimed MPG figure?

Why do cars not achieve the claimed MPG figure?

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Why do cars not achieve the claimed MPG figure?

Q. A Peugeot I test-drove recently claimed 90mpg; I managed 47mpg. Why the discrepancy?

CC, Chippenham, Wiltshire

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A. Car makers have become adept at designing to the laboratory test, which was last updated in 1997. They design cars with gear ratios and engine settings that will ensure a good result. The International Council on Clean Transportation says real-world and test figures now deviate by about 40%.

Hybrid cars can have even greater discrepancies than standard petrol or diesel-powered vehicles.

However, a new test is due to be introduced in 2017 that will more accurately reflect real-world MPG, with manufacturers forced to publish results.


Sunday Times Driving Car Clinic: Tim Shallcross, advance driving advice

Tim Shallcross used to train AA patrols to fix cars. Now he advises the Institute of Advanced Motoring — read more from Tim here.

Email your question to carclinic@sunday-times.co.uk or write to Car Clinic, Driving, The Sunday Times, 1 London Bridge Street, London, SE1 9GF, with a daytime phone number,
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