According to Robert Sikorsky, "Drive It Forever", "short trip" driving is the severest of all operating conditions...
He suggests not starting the vehicle at all unless you're going to drive it long and far enough to get the engine up to operating temperature and keep it there for 20 minutes, so that it is able to "boil" contaminants out of the oil.
As to "how much warm-up before getting under way", he also suggests that 20-30 seconds should be plenty - enough to get oil to all points of the oiling system. He recommends driving "gently" until the water temp is up to "normal".
Idling for more than a minute is probably worse than just moving the car across the street then shutting it down.
Sikorsky's theory is based on the idea that a cold engine is going to be running "rich" and "loose", and that there will be lots of blow-by and gasoline getting past the rings and into the crankcase... so if the owner has the choice of this "damage" happening while the vehicle is just sitting still, not doing anything useful, or going down the road and actually serving a purpose, he advocates that the vehicle do something useful, to "justify" the wear-and tear we've subjected it to just by starting it up in the first place.
It would be beneficial to your car to give it a good run at least once a week, for at least a 1/2 hour or so, to get it good and hot and "boil" the contaminants out of the oil and also "dry-out" the exhaust system.
Oil change every 2 to 3 thousand miles would also be good.
"Drive It Forever" is an interesting read, if you can find a copy...
Sikorsky is a member of the Society of Automotive Engineers, so presumably he's a little more scientific than the average hanger-on at the local garage...
For what that's worth...
Frank McMullen
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