How accurate are fuel economy figures?
Your motoring problems solved
Q. My wife has bought a 61-plate petrol Nissan Qashqai+2. Its fuel economy is typically 20-24mpg. Our trips are short so we’re not expecting the 40mpg-plus advertised, but surely something is wrong. DP, Glasgow
A. Car makers publish economy figures that bear little resemblance to real-world driving because the tests are carried out under laboratory conditions. We have highlighted the gap between advertised fuel economy and the reality many times — and moves are afoot to modify the official tests so they reflect true efficiency.
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In tests carried out by third parties, the Qashqai achieves 80-90% of the official figure. If you are getting significantly less than this, ask your garage to check that the right engine oil is being used, the spark plugs are in healthy condition and the air filter has been changed when it should be.
The most likely reason for your low figure, however, is the type of driving you are doing. A journey’s length, fierce or gentle acceleration, and terrain all make an enormous difference to fuel efficiency. If most of your journeys are short, the engine may not be warmed up and won’t be operating at peak efficiency. And short journeys are often made in traffic, with lots of stopping and starting, which reduces economy.
There are things you can do to improve efficiency. Look up the road and anticipate traffic-light changes, queues in traffic and other obstacles; if you slow down earlier you can often keep moving, rather than having to brake to a halt, helped by keeping a gap ahead of you. An advanced driving course will show you this technique as well as many other tips to get closer to that laboratory-generated fuel economy.
TIM’LL FIX IT
Tim Shallcross used to train AA patrols to fix cars. Now he advises the Institute of Advanced Motoring – read more from Tim here.
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your address and as much detail about your car as possible. We can’t reply in person, so don’t send original documents or SAEs. Advice is given without legal responsibility.
