Retardation or fact?

Defleshed said:

I was casually chatting with a friend of mine and something in the topic led me to say "yeah in winter i usually start my car up, and let it idle for a good 5 - 10 min before i jump in and drive so it gets warmed up". my mechanic friend said "that'll really mess your car up, you shouldnt ever let it idle like that, not with a 4.6 at least". what the hell? this is contrary to everything ive heard, and to all logic that i've come to know. does there any bearing or truth to what he said?

thanks.

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GTMomma02 said:

I thought I read in the manual somewhere that if your car will be sitting at an idle for more than a couple of minutes, it's better to just turn it off. Maybe not in the manual, maybe here on stangnet. Anyway, I know I read it somewhere, but like Premuim Speed pointed out, sometimes you sit in traffic for an extended period of time and your car still runs fine. I wonder what the deal is.

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merc123 said:

From what I understand letting the EFI car idle is causing wear and tear on the engine. ALSO, 0 miles = 0MPG. So it could also be an environmental thing to "improve" gas mileage.

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Huck said:

The issue...and it applies to all engines, EFI or carbed...is that most of your wear occurs in the first few minutes when the engine is cold and the parts have the most clearance (too loose). What you want to do is give it 30 seconds or so for the oil pressure to come up and everything to get circulating, and then start driving it - moderately. That way you bring the temp up much faster than you do with it sitting there idling (which, cold, is a very different thing from idling when at operating temp, and it can sit, in cold environments, for a long time without coming to operating temp - much more so than if you just start driving it), but you don't overload it. Then, when its up near operating temp, and all the clearances are much tighter and the wear will be less, you can start hitting it harder.

An issue that makes the wear issue worse - especially in choked carburated engines - is that the mixture is richer at idle when cold, and all that extra fuel washes down the cylinder walls and removes your lubrication, as well as diluting your oil. But this is much more of an issue with carbed engines than with EFI.

Taking it easy 'til its up to operating temp is a good idea. Letting it sit at idle, cold, and not warming up very fast, is a bad idea - and a waste of time and fuel. And letting it warm up in the winter for 5-20 minutes so you don't have to put your cushy ass on a cold seat has nothing to do what's good for the car.

All the above is why your owners manual DOESN'T tell you to "warm it up" for 5, or 10, or 20 minutes before you take off. Most manuals say to let the oil pressure come up for a 20 or 30 seconds, and then drive easily the first few minutes.

All that said, I know of LOTS of cars that get warmed up in cold climates for the comfort of the passengers, mostly without real serious wear issues (though most of them are not cars that are often driven hard) - though that's the worst environment to do it in. But if you're warming up your car several minutes for the BENEFIT of the car, and not your own comfort - you're wasting your time and gas, and actually doing what's NOT best for the engine.

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Huck said:

and actually doing what's NOT best for the engine.

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ADRENLN said:

i really think both ways is going to cause damage no matter what, and both ways are prob. so close in the damage they cause it really don't matter.

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Premium Speed said:

ding ding ding

to put it bluntly....IT DOESN'T MATTER!.........lol

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