Shutdown/Startup vs continuous idle fuel consumption
 

Assume I am driving a gasoline-powered fuel-injected 4-cylinder economy car.

Say I am in line at the drive-up window of a bank. There is a car ahead of me at the window, engaged in a long transaction. Will I save gas by shutting off my engine for a few minutes, then starting it again to pull up to the window?

Put another way: How much gas is used to start a fuel-injected engine, and roughly how many minutes of idle does that fuel represent?

A good basic rule of thumb for a gasoline engine is if you're going to be stopped more than 30 seconds, shut the engine off. 60 seconds for a diesel.

Thanks, this helps me as well. I have an automatic and I've been trying to figure this out.

Off every time i'd say, forget about timing it! Every car has start/stop built in now, and from experience, it shut's the engine off after about 7 seconds of idling in normal conditions, and starts again as soon as the clutch is pressed.

The only issue that that these new cars with start/stop have significantly upgraded starters because of the heavy usage. If you do this all the time with a regular car, you'll wear out the starter faster. 30 seconds seems like a good trade-off point to save fuel, but not be abusing your starter.

Perhaps cars sold in the UK are different, but here in the USA not all that many cars have automatic start/stop. In fact I'd say darn few do. I can also tell you that in Summer it would be mighty unpleasant for the air conditioning to shut off when stopped in traffic, and in Winter under some conditions the windshield would fog up or ice over if the defroster shut down.

Models equipped will be expanding in the coming years for the US.
Perhaps it will be selectable with an ECO mode or some such, but the default will likely be start/stop off with AC on.

News flash! Europe has weather too! ;) It's a very clever system actually.

Yes, I had heard. Europe sometimes gets the really massive storms after they're done with us. Sometimes the hurricanes even forgo visiting us and travel directly to the UK. When I was stationed in the UK, many moons ago, it constantly amazed me that British cars didn't like to run in the wet.