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"But today's computer-controlled fuel-injected vehicles automatically compensate for cold conditions so that is no longer necessary. The only reason to let them warm up is to get the heater up to operating temperature so the interior is nice and toasty before you take off. Lot's of people do this and that's their business, but it's not good for your car."
Nothing is being harmed by letting it idle the computer will control the combustion for you.
It can idle all day long.
Some diesels will/can experience cylinder wash down if let to idle at low temperatures for a hours.
The computer can even increase the idle speed to help control combustion temps if the temps fall below what the threshold is set at..
In the North land we sometimes idle them all day.
As a warm place can be a life saver in the winter.
A short drive will clear any condensation, carbon or fuel contamination in the oil.(the water will evaporate)
Idle speed can be from the lowest rpm to the highest rpm You can idle your engine at 700rpm or 3000rpm it's still idling.
If your experience has taught you all that you should stick with it. Meanwhile I'll stick with what my experience - 12 years selling auto parts and 30 years tearing down engines to observe firsthand the damage caused by different types of driving - has taught me.
If oil goes through the bypass in the oil filter, it merely bypasses the filtration material. Its path in the engine is unchanged. So "dirty" oil might flow. But I'm not convinced that with a proper selection of viscosity (according to manufacturer's rec) that the bypass would be used.
I used the wrong term not the oil filter bypass but the oil pump pressure relief valve.
Thick oil will cause a high oil pressure reading this does not mean oil is flowing.
as you can see in the diagram if the oil is thick and not able to pass threw the oil filter it will just be dumped back into the oil pan.
But I try to drive slow for the few minutes. Getting out of house for the first minutes are slow going narrow streets and traffic lights, so I think that's a good way to warm up my car while still going where I need to go rather than wasting gas and time idling.
If your experience has taught you all that you should stick with it. Meanwhile I'll stick with what my experience - 12 years selling auto parts and 30 years tearing down engines to observe firsthand the damage caused by different types of driving - has taught me.
Your right my 34 years as a wrench turner and equipment operator have thought me this
from working in sub zero temps for prolonged periods of time.
In most cases, practical conditions will make it necessary. Start the car and let it warm up while you are going around outside the car scraping the frost and snow and ice off the windows, and get the defroster blowing hot. If it's not cold enough to frost, it won't need to be warmed up.
I don't know if this is typical of many cars, but my Toyota Previa would not shift into overdrive until the engine warmed up, at least to the point at which the Temp gauge needle moved off C. And the radiator warmed up a lot quicker idling than while moving . If I tried to drive when still cold, it would not shift up to OD, and it took a long time for it to get warm, so it ran at high rpms until warm.
There are a few issues; probably the biggest is that when an engine sits overnight and cools condensation causes moisture to get into the oil. When the engine is quickly warmed up to operating temperature - which is what happens when you get in the car and drive - the moisture burns off and changes the makeup of the oil very little. But when the engine is slowly warmed up - whish is what happens when you let the car idle - the oil/water mixture is "slow cooked" into a nasty substance called sludge. This gunk will stick to the internal surfaces of your engine, and can eventually dry out and flake off. The flakes can plug oil passages, which can starve the crank and rod bearings of lubrication.
When is sludge not sludge?
Easy; when it's an oil and water emulsion
There's a snappy new moniker for Black Death now, and it's called sludge. The cause is the same as Black Death and it seems to be regardless of maintenance or mileage. The chemical compounds in engine oils break down over time due to prolonged exposure to high temperatures and poor maintenance habits. When the oil oxidises, the additives separate from it and begin to chemically break down and solidify, leading to the baked-on oil deposits turning gelatinous, and that nasty compound is what is lovingly referred to nowadays as sludge.
Myth: Shutting off and restarting your vehicle is hard on the engine and uses more gas than if you leave it running. Reality: Frequent restarting has little impact on engine components like the battery and the starter motor. Component wear caused by restarting the engine is estimated to add $10 per year to the cost of driving,
No thanks I'll spend the $10 on fuel.
Last edited by snofarmer; 01-06-2012 at 11:21 AM..
Your right my 34 years as a wrench turner and equipment operator have thought me this
from working in sub zero temps for prolonged periods of time.
If we're talking specifically about sub-zero conditions I will agree with you.
The potential for damage due to lack of lubrication from operating an engine under a load when the oil is too thick to flow is greater than the potential for damage due to sludge in the oil. At those temperatures you also want to make sure you aren't going to have an issue due to moisture in the fuel; better to be stranded at home than out on the highway. And sitting in a car at 20 below zero while driving down the road as it warms up is a health hazzard, not just a discomfort.
Where I live I might have 10 sub-zero starts a year, and on those days I actually start all 3 of our vehicles and let them run 10-15 minutes whether we anticipate driving them or not just so we know ahead of time if they're going to function, just in case we need them.
But on typical cold mornings in the US (say 5-32 degrees) I do think a person is better off limiting their idle time, unless of course they have an issue with a specific vehicle that won't function properly until it reaches operating temperature such as in jtur88's case.
Does the coolant temperature have anything to do with warming up a car? My dash displays the coolant temperature. I usually wait until it's at least 100 degrees then drive. Should I wait longer or not pay any attention to that? I drive a 2008 Cobalt. It's parked in my garage overnight. My typical commute is 4.2 miles and I don't go above 50 mph. During the winter, morning outside temps are around 25-35 degrees.
eggalegga, what you are doing is just fine.
Yes the coolant temp is related to your engines temp.
100* is fine 190* -195* is optimum for a gas powered vehicle.
Even with Synthetic 5W-40 oil in -50*f temperatures the container was actually pity solid, it flowed like thick pudding.
My experience is when I drive off the street I live on and depending which way I'm traveling, I can be driving at 55 mph plus is less than 30 seconds. I prefer (especially when cold) to let it warm a couple of minutes.
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not the oil filter bypass but the oil pump pressure relief valve.
