<MISC> re: Warm Up Before Driving

[Christopher Pawlowicz <chrisp@xxxxxxxxxxxxxxx>]

Murray sez
>My owner manual says NOT to run the engine a long time at idle just to
>warm up the car. I think it suggests a max of 30 seconds or something
>low like that. Obviously, no-one at BMW has had to wake up to a frigid
>car in frosty Calgary.
>
>Does the BMW caution against long idling (to warm up the car) arise more
>from an environmental concern, or is there a valid and important
>MECHANICAL reason for this?
>

two main things I can think of for bmw's (and all car manufacturers) reasons:

1) if you let the engine warm up and get nice and toasty and then drive
 away thinking 'I can zoom right along now 'cuz everything is warmed up'
 you are forgetting the fact that the rest of the car is ice cold
 (transmission, differential, wheel bearings, etc) and they will suffer..

  if you get in, start up, and drive away at a reasonable speed, everything
 warms up together in a nice controlled way all at the same rate

 also, the engine will warm up much quicker driven under a little bit of load..
 much faster than letting it sit there idling

2) environmental concerns.. who needs tons of cars sitting there idling,
 especially when cold, running rich to keep the car from stalling etc.


that being said, YA, RIGHT! when there is an inch of ice and snow frozen to
the windshield, or heck, even a light drizzle of freezing rain or maybe a bit
of snow, you *can't* drive unless you have heat blasting out of the
defroster vent.. even when you scrape off all that crap you need heat to
keep new ice from forming..

and the only way to get heat blasting out of the vent is to let the car idle
until it gets warm..

so take bmw's advice with a grain of salt..
yes there are reasons, but sometimes you just gotto do what you gotto do.

Chris Pawlowicz
(Ottawa)
'89 325i - 290k km
'74 2002

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