Submitted by giuliomagnifico t3_yk2sm8 in science
Reply to comment by colem5000 in 30 minutes of car preheating in sub-zero conditions produces as much particulate emissions as driving 97km in a gasoline car, or 20km in a diesel car “These findings do not suggest to stop preheating cars; instead, we could reduce the emissions by using similar methods that are in place for engine” by giuliomagnifico
The best way to warm up an engine is while under gentle load.
Even if you don’t use top-tier boutique synthetics, any modern API-rated oil will properly lubricate the engine for the vast majority of us. If you live somewhere really cold, where it gets we’ll below zero Fahrenheit, an easy solution is to use a full synthetic, meaning at least a good Group 3 oil, 0W-XX oil.
An oil’s pour point isn’t a great indicator of whether an oil will pump adequately upon startup, but it does show you that even a decent synthetic like Mobil 1 10W-XX oil will still pour at -39C. They offer other synthetics that are down in the -50s C.
Sitting there idling your engine to warmup also prolongs the time it takes for the oil’s viscosity to reach the point where wear is minimized. Regardless, at the temperature most of us experience during the winter (positive degrees Fahrenheit), the wear on your engine will likely not matter in a practical sense. Lubrication IS happening. The thought that you’re running your cold engine dry for some period of time is simply not true.
Anecdote: we get into the negative teens Fahrenheit for at least a few days each winter where I am most winters. Even still, my oil pressure light goes out nearly as quickly as when it’s warm out. The oil pump does have a bypass, which will open when the oil is very cold and thick; however, the pump is positive displacement and an adequate amount of oil will pump to the supply channels almost instantly. That’s. It even to mention the leftover film of oil and boundary layer of additive protection left on the bearing surfaces.
Ok you start your engine at -40 then drive it instantly and see how long you engine last. While your driving your running at a much higher RPM then idling. All that extra wear will cause premature engine issues. You do what ever you want. I will continue to warm up my engine before I put them under load.
You’re talking things way out of context and exaggerating the risk. Much higher RPM? Most cars cold idle at 2K RPM as is. I’m advocating driving off gently, not starting up at low temps and gunning it immediately onto the highway. Besides, I’d argue that overloading an excessively cold engine is more likely to result in catastrophic failure such as a cracked head, blown gasket or spun bearing. Who cares about wear at that point?
Also, did I even mention doing this at negative 40? I was pretty clearly stating that most of us start and drive our vehicles at temperatures at which the oil is immediately properly lubricating the engine, far from the limit of the oil. On the flip side, just as your example of loading up an engine at negative 40 is absurd, so to is warming up your engine by idling at, say, 0C.
Most of us, including me, never even see close to -40 where I am. As mentioned, I RARELY see below zero and never below the negative teens Fahrenheit, which I think is pretty common. Under these circumstances, starting up and driving off gently is the best thing to do.
As mentioned before, the only way to warm up the rest of the drivetrain is by driving. I think that’s neglected, and some who warm up their engines have no problem loading up the rest of their bone-cold drivetrain. If you do idle your engine to warm it up, I hope you at least still drive gently for a bit to warm up the rest of the car.
I get it, though, it’s human nature to want to take care of things that are so important to us and cost so much money. But, just because you think your engine is as cold, brittle and sensitive as you feel doesn’t make it actually so.
Finally, I don’t begrudge anyone who wants to warm their car up for personal comfort. I think it’s wasteful and polluting, but we all do things in our lives that pollute and we can improve on, so who am I to give someone a hard time. If the conversation comes up, however, I will make it known that warming up an engine for the engine’s sake before taking off is all for their peace of mind only the majority of the time.
Who warms their vehicle up when it isn’t negative temps? That is a complete waste of time and gas. Well where I live it gets to minus 40 every year and averages around -20 all winter. That’s what warming up an engine means to me, not at plus 2. So yes I guess your right at the temps your talking about it’s fine to drive to warm up your vehicle but not in the winters where I live.
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