OK I got a debat whit my girlfriend and a couple of friend about this topic...

First: Does a gazoline car really burn 1L of fuel when you start it...

Second: how much gaz does it burn if you let it heat up (in cold weather) let say for 15 min. a lot or not much?

Third: if I put the heater on does it burn more fuel.

Tanks for shutting them up! Heheh:D

Nope, they do not use a liter of fuel just starting, only about an ounce at most. Letting a car idle for about 15 minutes could use about 3 oz. more. Yes you will use more gas with the heater fan running but only very little. The fan motor puts a draw on the battery and the alternator then puts a slight load on the engine causing it to run a bit harder.