UK Car Repair: Automobile fuel usage, automobile fuel, modern cars

Question
when waiting in line at a drive thru,do you burn less gas stopping your engine and restarting as you move up in line or letting the engine just keep running?

Answer
If you turn off the engine you will save fuel. On modern cars especially, no more fuel is used to start than to idle. On older systems with accelerator pumps usually a little more fuel was pumped in to aid starting, even then, it was a less than the engine would use in about 20 seconds, so- depending on the time switched off- still saving some fuel.  The down side could be overuse of the starter and battery.  This is something I do if I can see the wait is going to be over a minute or so.