Car/Truck idling misconceptions

[loudist]

"Engine Wear and Tear
Letting an engine idle actually does more damage to the engine than starting and
stopping. Running an engine at low speed (idling) causes twice the
wear on internal parts compared to driving at regular speeds, which
can increase maintenance costs and shorten the life of the engine.
Generally, fuel consumption during engine start-up is equivalent to
about 30 seconds of engine idling."

From: EPA New England

Something fleet mechanics have known forever.

Some folks believe that there is a linear correlation with hours idleing to driven mileage (or engine hour run time), where there are many more destructive variables involved with idleing hours than driving or running the engine at an efficient rpm and load.
One destructive variable is condensation in the exhaust and also into the crankcase, which builds up acids, which are destructive to the exhaust system as well as the internals.
The enging temp is lowered at idle rpms, the condensation does not cook efficiently out of the oil causing sludge.
Inefficient combution results from lower cylinder pressures causing carbon buildup in the top end sparkplugs, valves, o2 sensors, while also finding its way into the crankcase through blowby causing accelerated wear. The increase in pollution from this is up to 10 times the pollution from an engine under driving conditions.
Lowered oil pressure from idle causes less hydrostatic pressure on bearing surfaces increasing oil shear and consequently wear.

Excessive idleing is very stressful to an engine and related systems.

Fleet owners are now starting to require that truckers reduce idleing of their trucks by sustantial amounts (there are now idleing monitors that can be installed) to save on fuel and maintinience costs. The side benefit is cleaner environment.

Of course there will be a$$brains that will think that 'hours are hours' no matter what rpm.

 

[John K]

Everything I've read agrees with your post, but people want to get into a warm car on cold mornings and also believe it is better for the car to warm up first. That myth is hard to stamp out. There have been many posts here about it. I expect it was much worse on cars with carbs, before the computers that backed down the idle speed as it warmed up. Imagine what the excess gas from heavy chokes does to the cylinders....

 

[TheTanSedan]

Extensive idling is alike to smoking in a restaurant. No one likes it (except the guy idling), and it worsens the atmosphere for all.

Here in Dallas (nations hottest big city by virtue of Temp/Humidity Index), one sees cars idling for extensive periods all the time . . . unlike pre-1980 when lack of computer-control made extensive idling with the AC pretty much the exclusive domain of well-tuned 440-500 cid full-size cars (aahhh, big ol' Cadillac, Harrison A-6, and that incredibly well-set factory QuadraJet.) The old AC compressors were power hogs.

Up to about 15-minutes of stop time, when idle speed has been held to a point high enough to keep oil pressure above, (say 40-psi), I doubt the wear problem is significant to any degree.

But after that cool-down transient is past (vehicle temps spike momentarily and heat is then slowly released) then, yes, the wear-and-tear is (ought to be) unacceptable . . . and the further pollution increase is unacceptable in any major metro area for the "comfort" of one or two people otherwise too lazy to get out of the car.

Is there a better argument for federal funding to seriously studying and bettering traffic flow than the inclusive costs of idling on time lost, health worsened and the individuals' increased lifetime capital outlay vis-a-vis cars wearing out too soon? Jane Jacobs makes the point that traffic engineers in no way have made a solid case for bigger roads (The Death of American Cities, and, more recently, The Coming Dark Age); literally, they have no proof for their assumptions about traffic flow. By itself, idling is but a part of a larger picture.

We, as a society, ought to at least get rid of drive-thru "convenience".

Obviously, hybrid cars that "idle" on other than internal-combustion power are a step in the right direction.

As for BITOG guys, the wear of idling, or, alternately, stopping/starting the engine is somewhat alleviated by a low-restriction oil filter (in Terry Dysons words [old post] "screen door on a submarine"); by the use of FUEL POWER and LUBE CONTROL, by scheduled UOA, and, obviously, keeping all engine [accessory] systems in best possible shape. The bypass guys have a real leg up here.

[ March 18, 2005, 11:32 AM: Message edited by: TheTanSedan ]

 

[Colt]

quote:

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Originally posted by John K:
Everything I've read agrees with your post, but people want to get into a warm car on cold mornings and also believe it is better for the car to warm up first. That myth is hard to stamp out. There have been many posts here about it. I expect it was much worse on cars with carbs, before the computers that backed down the idle speed as it warmed up. Imagine what the excess gas from heavy chokes does to the cylinders....

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I agree.
Hence the remote starts in my daily drivers.
A 5 minute warmup is fine