every morning i start my car 15 min. before i go to work (anyway it's better for the car to).
Ummm... there is room for argument there.
What damages a car in cold weather operation is running the engine at less than optimal temperature. The longer you run it "cold" the more damage you do. The fastest way to get the engine warm is to drive it. You are probably running the engine for twice the number of revolutions to warm it up by idling it than you would by driving, not to mention the fact that the time spent idling is wear on the engine with no productive use made of the running time. In other words, you idle it 15 minutes, then spend 15 minutes driving to work -- you've doubled the running time and the engine wear for the trip.
Now, the above argument assumes that you are starting a somewhat pre-warmed engine (block heater, and oil pan heaters on the engine and transmission) and that you are not using heavy throttle loads immediately on starting off. Under those conditions, the engine will reach optimal operating temperature in as few as 3--5 minutes, as opposed to running 7--10 minutes with improper (cold) engine clearances at idle.
One of the best "engine savers" I have found is an electric interior heater that warms the interior while the block heater warms the engine. When you come out of your house and it's 25 C below zero, having the interior of your car comfortable reduces the temptation to start it up and let it idle. Not to cast any aspersions here, but I have found the great majority of people who rationalize that they are babying their car by idling their engines for extended periods of time in cold weather are really just babying their poor cold tushes!
Well, if this post doesn't get a mini-flame war started, then I've seriously mis-estimated my fellow bbs posters!
tanstaafl.
"There Ain't No Such Thing As A Free Lunch"