This is a tough question, because it depends on where you are, what type of car you're driving, and how cold it is outside. different experts have different opinions about this topic too. to give an exact answer, i would need more information about your circumstances. so if you could provide tidbits like that in the comment section below – maybe in one sentence or two at the most – then i'll take a stab at answering this for you…
the best way to warm up your car's engine before driving is to drive it for five minutes so the oil circulates through the engine. this prevents any uncomfortable ‘cold starts' when trying to move forward too quickly out of traffic or work parking lots. while
how long does a car need to warm up?
this varies substantially depending on your vehicle. cars with a diesel engine take much longer to warm up than cars with an electric or gasoline-powered heater (roughly 10 minutes for each mile driven, or 10 minute interval). however, when the weather is around freezing and the car's battery has been left dead in the morning it may take 2 hours to sufficiently warm up. vehicles also vary in this respect and some will be more efficient at warming themselves than others (i.e., an old soviet car might still be cold after 5 minutes while a new bmw may not even need 5 seconds).
nevertheless, all of these factors can easily be checked by looking at your owner's manual which will list specific recommendations about how long you need
what happens if you don't warm up your car before driving?
warming up improperly is an incredibly bad idea for safety reasons. the alternator needs to be running just enough to keep the battery charged and, if you don't allow it to build up power before driving, then you could find yourself stranded on the side of the road or severely damaging your battery – cold engines use more fuel than warm ones too. finally, if you realize 5 minutes down the road that you forgot to turn on your headlights (it really happens) but didn't want to turn around and head home because who knows who might pick one open later in broad daylight, then at least make sure you've got a full tank of gas; idling for too long will deplete your car's fuel reserves.
why you shouldn't warm up your car?
it's not clear what you mean by the question, but based on our understanding of your question, it would be wise to turn on the engine for a few minutes before driving.
in very cold temperatures, objects naturally calcify from contact with liquid suddenly turning to ice. if those objects are engines and fuel lines as they start, the lines may freeze and result in insufficient fuel delivery or loss of power when starting. in some instances this can cause an unsafe situation where a vehicle stalls onboard a roadway due to insufficient gasoline associated with warming up the vehicle before use.
we recommend warming up your vehicle prior to taking off by running it for a few minutes first. this will allow time for any liquid that is present under either of those components