What are the benefits of idling your car in the winter at cold start when it is known that engines wear less if the car is moved right away at low RPM?

Answer 1

Even though I'm not a Canadian and not living in Canada...I do however live in the Northeastern section of the US, were winter temps can reach as low as -25 deg. f. When being concerned about oil related conditions, wind chill isn't a factor, only ambient temp. Watching the oil pressure guage at cold start-up, the reading is near max pressure at idle. With that said, some oil may be beginning to bypassed the main oil circuit back to the oil pan at the pump. This is to help prevent over pressurization of the lubrication system that can lead to filter bursting, blown gaskets, and broken pump shafts to name a few things. As I have read that oil pumps are a volume device rather than pressure device, pressure is built as there is resistance to the flow of fluid for which it pumps. Cold oil is appearently thick oil (ever do a freezer test on a small vial of oil?), and as the oil pressure may already be causing max system pressure at idle, that means oil flow within the engine's pathways is slow to move and pass through the clearences of the bearings, etc. Reving the engine any higher doesn't cause more oil to flow through the pathways if the pump's bypass is already starting to open, but rather it just leads to more oil being dumped back into the oil pan at or near the pump. This could lead to lubrication starvation, and is thought to be the reason why some newer cars as I've heard (German make I think) are starting to have a varying redline indicator. In such a case, the redline would start out low until the engine and oil were up to temp, for at which time the redline would have graduated up to it's normal rating. Another take would be the psychological association of human to machine - call it embodiment or projection of condition. Would someone want to jump out of bead and head right into the cold to shovel a driveway full of snow on a bitterly cold morning? I wouldn't. I'd take my time getting ready, getting something warm to drink and eat, etc., and then venture outside after getting bundled up and ready for it. Just starting an engine that's been out in the cold, be it in a vehicle or the pull start snow blower, it just resists (like one getting out of a warm bed). The engine may buck, vibrate, and just plan fuss...that is until you give it some time to warm itself up. I usually start the engine and move on to other preperations like cleaning the snow of the car, shoveling a way out, etc., before I finally get it in gear (seems productive as far as time management). And even so, the oil pump is still going into bypass before the automatic transmission shifts into the next gear on my vehicle. Other then those who take short trips, I see nothing wrong with a short warm-up period of say a few minutes in the cold of winter, to as little as 20-30 seconds in the heat of summer. What condensate is formed on the oil will be boiled/burned off if you get the oil up to running temperature and hold it there for 20-30 minutes. Engine oils by design also contain additives that help control possible side affects related to condensation and fuel dilution such as acids and particulate matter, albeit to a degree. So within a reasonable oil change period things should be fine. And just what is a reasonable oil change interval you ask, well that depends on a lot of factors really, but for which I have seen that only oil analysis can give you the best indication thus far. Some newer vehicles are now coming out with passive/active monitoring systems that calculate for the driver when the next oil change is recommended. Well, not so much science I have given as it is nothing more than opinion and observation...so take it for what it's worth. "Where's the documented proof to back-up the 'known fact' that engines wear less if you move right away at low RPM after a cold start?"