Better to warm up a car in a garage or on the road?

Dear Car Talk

Dear Car Talk | Oct 01, 1996

Dear Tom and Ray:

My drive to work each day is less than a mile from my home. Because I often
work at night, walking is out of the question. My husband tells me my car
should be "warmed up" longer than it takes me to drive to work (which takes
about four minutes). Is it more beneficial for the engine if I were to
leave 10 minutes early and take the "scenic route" to work, or let the car
warm up in the garage for several minutes? I understand that excessive
idling isn't the best thing for the car either. What would you recommend? -
- Dee Dee

TOM: Gee, life IS complicated these days, isn't it, Dee Dee?

RAY: Here's the deal. One of the worst things you can do to a car is run it
for just a few minutes. When you do that, you generate moisture, but you
don't let the engine get hot enough to burn it off.

TOM: So the moisture seeps down past the rings into the crankcase and
dilutes your oil, and it collects in the exhaust system and promotes rust

RAY: So it IS a good idea to let the engine heat up and reach operating
temperature. And as you've figured out, there are several ways to do that.

TOM: Taking the scenic route to work would be the better method -- from the
car's point of view. The car warms up faster when it's being driven, as
opposed to just idling in the driveway.

RAY: On the other hand, taking the scenic route to work is inconvenient,
not to mention wasteful. And the scenic route does lose some of it's "je ne
sais quoi" when you're driving at night, wouldn't you say?

TOM: So I'd go for a compromise position, Dee Dee. In addition to your
short trips to work, make sure you use the car for your longer, half-hour-
plus trips on the weekends. That'll give the engine a chance to heat up and
vaporize the excess water you've been collecting all week.

RAY: Maybe you could volunteer to do all the carpooling on the weekends --
even if you don't have kids!

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