Why are the engines let to run a while before moving?

Stupidity mostly. Same reason people buy remote starters. Even a thought of minor discomfort makes them uncomfortable.

Regards,

Boris Mohar

Got Knock? - see: Viatrack Printed Circuit Designs

Ignorance, or maybe they enjoying burning fuel un-necessarily. The best and fastest way to warm up an engine and transmission is to *drive* the car, gently during the first few minutes.

With an old car and no heat riser it helps keep it running. I take off as soon as I think it will pull a load up the hill without lugging badly. In winter it takes no extra time because it takes that long to clean the windows.

With a diesel you need to let the engine warm up. Especially when it is cold out. The engine needs the heat to run. This is especially true for older car as some one already said. Some people do it so that the inside is nice and warm for the winter and nice and cold for the summer. Other than that there is no need to.

Tim

Clean the windows??? Don't you just chip a clear spot the size of a dime and go ripping along at the posted speed limit? (LOL) I would say that you don't have to idle for a few minutes but more like a few seconds to let the oil get flowing. Then drive easy for a few minutes for the tires to round out and the suspension to unfreeze.

I haven't seen the obvious reason of allowing the oil to begin flowing across the engines upper components thoroughly before revving the accelerator posted yet. Also, before leaving, isn't a good idea to just listen to things before darting off? I mean it's not a passenger jet or anything but I take a listen before I go running off and check the gauges. Just functional checks in my case before I get too far away to do anything about it.

PP wrote:

"ed" wrote

What obvious reason? How long do you really think it takes before oil "begins flowing across the upper components"? Folks make it sound as though it's minutes before oil gets to the valve train.

I don't want to listen to my Dodge 2.5 liter hammering away in the morning......so I have the fan turned up and radio full blast.

Ian

I am glad that you said that it was mostly stupidity. Around here, there are winters that are severe enough that you cannot defrost the windshield before the thermostat opens. I have also had the misfortune to drive vehicles that will stall/flood while cold (my worst winter vehicle had a broken throttle linkage with no fast idle cam, so I had to sit in my freezing cold vehicle, with my foot lightly pressing on the gas, or it would never warm up [once given a good heat soak, parked out of the wind, it would still be warm for hours after shutdown, though]).

Some cars run for over 300000 miles. Why? because these smart people give their car 15 minutes to warm up. moving metal parts need lubrication. duh.

"robertmaasjr" wrote

Ahhh...someone who has no clue how engines or their lubricating systems work.

Ian

Idling for 15" is excessive enough to damage a converter in earliar models without feedback controls, but who has a converter anyway? A couple minutes is sufficient.

If by "give their car 15 minutes to warm up" you mean that they drive moderately, not using full throttle and not exceeding, say 3000 RPM, then you are correct. I like to see an oil temp of >90C before driving a car "hard." However, if you "warm up" a car by idling it for 15 minutes in a driveway, that's bad advice - while the engine oil may be warm after that, wheel bearings, transmission, etc. will still be cold. In fact, ISTR a discussion of this on the ACVW newsgroup, apparently there's an issue with long idling periods when cold and insufficient/too cold lube getting to the tranny mainshaft bearings, which can actually cause premature wear.

Well, 15 minutes is ridiculous. But not as stupid as people that jump in a stone-cold car, drop it in gear as soon as they release the key, pull out of the parking lot, and hit redline twice merging into traffic rather than letting it idle for 30 seconds after start-up and then staying in the slow lane for a couple of minutes.

Metal parts change size as they warm up, no matter how "well engineered" the engine is. The fact that a modern EFI car won't backfire and stall when abused that way is no excuse to do it.

Agreed. And one of my cars is quite capable of blowing off an oil filter if revved above 4000 RPM before the oil temp is up!

Not to mention the fact that the oil is now full of fuel (both partially burned and unburned), water, and other combustion by-products due to the excessively slow warm-up period and poor ring-to-cylinder sealing when cold and un-loaded.

Approximately 11/11/03 15:39, robertmaasjr uttered for posterity:

Oddly enough, duh, a significant cause, duh, of excessive wear and outright breakage, duh, of suspension parts and drivetrain parts located away from engine and exhaust is just those same people who go "duh" all the time and drive away with a warm engine, duh, and cold suspension. So duh, so duh so duh. The only way to warm up those parts is to drive...slowly and carefully, for the first coupla miles.

"Steve" wrote

Other then hitting the redline twice (I don't ever do that as the car will shift before hitting the redline) I do and have done for years exactly what you describe. The only time I let the car warm up is when my wife is traveling in my car, she does not like jumping into a cold car. It doesn't do any harm to start a car and drive off.

Well, thanks for the quick and dirty lesson in "metal parts changing size as they warm up"......

What does that have to do with anything, other then you may have it ingrained in your mind that a car needs to sit and idle for 30 seconds before moving off? There is nothing abusive about starting the car, and just driving off like you normally would in the summer time....unless you happen to be in the habit of rally driving the instant you leave your driveway in the summertime.

instead of being sarcastic , you should have answered my question on installing a keyless entry system. i bet you feel foolish now.

I know we live in a free society but I don't think people like you should be allowed to voice such harmful statements.