Cost to coast

Over the past 30 years or so I have been in the habit of coasting down long hills in neutral with the engine idling. Can coasting do any damage? I find it suits my relaxed style of driving and as I recall many cars used to be fitted with freewheels anyway.

Asked on 28 August 2010 by WL, Oxton

Answered by Honest John

This is archaic thinking from the days of carburettors. Coasting with the engine idling in a fuel-injected car actually costs you fuel. For the engine to run at idle it needs a fuel supply. If you drive down the incline with your foot off the accelerator, the wheels turn the engine and all its ancillaries without any fuel being used at all. This is the case for all modern fuel injected engines whether petrol or diesel. I've just averaged 64.2mpg over 122 miles in my FIAT 500 1.2 petrol applying these techniques. Obviously doesn't work with an automatic. See eco-driving video at: www.honestjohn.co.uk/news/green-motoring/2010-06/r...1

Tags: coasting driving driving techniques

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