12 Jan 07
An AA team led by senior research engineer Peter De Nayer once figured out that a car gets through 15-25ml of fuel every minute on tickover.
If you're halted by 15 traffic lights on your morning commute, and you average a one-minute stop at each, that's three-quarters of a litre burnt daily without purpose. Which is somewhat wasteful.
Just killing the engine could end that waste immediately, but there are times when we shouldn't do it.
Cold cars won't like it, because so much more energy is needed to crank the engine through the still-chilly oil. And if it's only a brief halt, the size of the electric jolt required by the starter motor is greater than the amount of fuel saved: the battery will demand that back from the alternator, which in turn puts a greater load on the engine, which uses more fuel.
I tell you, balancing out the energy equation doesn't half make your head spin.
