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In practice, that does not hold true for a number of reasons. First, the inside air in the car is more humid than the outside air, because of the introduction of respirating thermoregulated mammals holding cups of hot coffee, and the fact that the air inside the car overnight is more humid air from the day before. So there is a substantial lag time before an AC defroster can reduce the humidity of the entire carful of air.
Defrosters that I've seen tend to spray a narrow stream of air onto a small strip of windshield close to the vent, and it can be several miles before a wide space in the driver's line of sight is affected by the flow. It is unlikely that the cold defrost will clear a safe viewing space before the heater air warms up.
You live in freaking Texas. Stop lecturing people about extreme cold weather driving!
In Germany (cold winters), nobody warms up their cars. It is actually illegal. You are not even allowed to let the car run in the winter while you scratch the ice off the windshield. So you clean the windshield off as good as you can, get in the car, open the windows to see out the side and drive to work, hoping the windshield thaws fast, while blasting the heater, who of course, takes a while to blow warm air.
I live in CA now and I am shocked to see how long people let their cars idle, to warm up, while they are in the store, while they have breakfast, or just for no reason at all.
Warming up a car is essential for the long term health and longevity of it..
At least 2 min during summer, 5min in cool weather and 10min in freezing weather..
Nothing personal, just grabbing one of a number of posts that express this same view... which many experts in the field say is incorrect.
For example, here's Tom and Ray, from Car Talk
Quote:
Ray ... On modern, fuel-injected cars -- basically anything made in the past 20 years -- you're not helping the car at all by warming it up for five or 10 minutes.
TOM: On older, carbureted cars, that kind of extended warm-up can actually cause damage to the engine by diluting the oil with excess fuel. So it's even worse if you have a really old heap.
RAY: But with modern cars, all you're doing with a long warm-up is wasting gas, increasing pollution, raising the temperature of the planet and making yourself 10 minutes late for your chiropractic appointment.
The proper procedure is to start the car. If it starts and keeps running, put it in Drive and go. Go gently (don't back out of your driveway and floor it right onto a highway entrance ramp), because you'll be warming it up during your first few minutes of driving, but DO drive it.
TOM: If it's bitterly cold out, like 10 or 20 degrees Fahrenheit or lower, you can let it warm up for a minute or two to allow the oil to thin out a bit and circulate completely. But other than that, if it runs, driving it gently is the best way to warm it up.
There are a lot of myths concerning the risk of damage if you don’t thoroughly warm up a cold engine, but most of them are just that — myths.
Modern engines are built to a much higher standard than engines of 25 years ago, and you can’t compare a 2012 Prius — or even a 2002 Camry — to a 1987 Toyota Tercel.
The best bet? Even if it’s just 10 degrees outside, start your car, let it run for 30 to 60 seconds to get all the fluids moving, then drive off gently.
Don’t race the engine or accelerate suddenly. Compared to idling in your driveway — where you get zero miles to the gallon — your engine will warm up faster, your exhaust system will get up to temperature faster so the catalytic converter can do its thing, and you’ll use less fuel. Which is what you wanted all along anyhow, right?
Myth: Wait, it's still warming up
Some people insist that your car will last longer if you let it idle until the engine reaches normal operating temperature.
It's true that running cold is harder on an engine than running warm. The oil is thicker, and it takes a little time - very little, really - for it to flow to all the parts of the engine that need it.
But letting the car sit while the engine is running doesn't help anything. It just wastes gas and pumps out needless fumes. You might as well get on your way.
All you need to do is drive your car gently until the engine is warmed up. No smoky burn-outs first thing in the morning. Just go easy and keep those engine RPMs down until everything's toasty, and you'll be just fine.
Five to ten minutes of easy driving is about all it takes before most cars are ready to rev, says Sinclair.
I don't see a problem with warming up a car before driving off and I don't believe it does any harm to a modern engine. Likewise, I don't see a problem starting it up and driving off right away either. Thats what I usually do. However, with these extremely cold temps we are having and my absolute hate of the cold I have been starting my truck up a good bit and going back inside so it will be nice and toasty when I get back in to drive away. My wife gets off work, usually between 2:30 and 3:00 AM, so I have been going outside between 2/2:15 to start the truck and go back in the house while the inside warms up and wait for her to call me to go get her. Yea, it's running for quite a bit before I drive off. I can walk the 30ft or so to my vehicle and back no problem but I hate driving off in a freezing cold vehicle so I'll do whatever to make it nice and toasty before hand.
I had a neighbor like that. I wanted to kill him every night when I had to wake up when he started his truck. Then I almost fell back to sleep and woke up again when he drove away 15 minutes later. But hey, at least he had a warm truck when he left, who cares if neighbors want to sleep.
Marlinfshr, nice gesture to your wife, but I hope your neighbors live a bit further away.
I had a neighbor like that. I wanted to kill him every night when I had to wake up when he started his truck. Then I almost fell back to sleep and woke up again when he drove away 15 minutes later. But hey, at least he had a warm truck when he left, who cares if neighbors want to sleep.
Marlinfshr, nice gesture to your wife, but I hope your neighbors live a bit further away.
If the truck was a diesel then he was doing the right thing. Diesels absolutely do need some period of warming up before you can start loading them. They rely on heat from compression (no spark plugs) and thus are very temperamental when cold. In the cold, my diesel gets 3 to 5 minutes of high idle before I start off on my drive.
I had a neighbor like that. I wanted to kill him every night when I had to wake up when he started his truck. Then I almost fell back to sleep and woke up again when he drove away 15 minutes later. But hey, at least he had a warm truck when he left, who cares if neighbors want to sleep.
Marlinfshr, nice gesture to your wife, but I hope your neighbors live a bit further away.
My truck is a modern smaller V8 gas engine 1/2 ton with intact exhaust. My car is a 2 year old tiny 4 banger. The only way you can tell either is running if you are more then 30 ft away is by seeing the exhaust. They are very quiet. My life actually goes on after dark. My wife doesn't drive yet so I have to get her late at night and in season I'd leave the house at 3 to 4 AM most days to go fishing.
More noise is made by pulling in or out of the driveway, which must be done, then letting my truck idle for a while, which I admit is my choice. Besides, me driving away comfortable in a warm truck with clear windows is a lot safer for me and anyone else on the roads then me driving away cold and shivering in a truck with fogged up and/or semi iced windows. So as long as we continue to get sub and super sub freezing temperatures I am going to continue to warm up my truck or car, whichever I take.
When I drove carbureted engines I certainly let them warm up in the winter. I would manually adjust the choke to keep it from nearly stalling, but it still needed a warmup for a few minutes.
With EFI I never warm it up; just start it, run it about 10 seconds and go. Never had a problem and I keep my cars for awhile.
In practice, that does not hold true for a number of reasons. First, the inside air in the car is more humid than the outside air, because of the introduction of respirating thermoregulated mammals holding cups of hot coffee, and the fact that the air inside the car overnight is more humid air from the day before. So there is a substantial lag time before an AC defroster can reduce the humidity of the entire carful of air.
It's a largely incorrect assumption anyway. The AC compressor cycles when the defroster is on in order to keep the system lubricated and keep the seals from drying out during the winter when the air conditioning isn't being used. It doesn't run long enough to have any impact on the air moisture in the air being piped into the cabin; it just kicks on for a few seconds at a time.
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