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gathermewool t1_iurcsis wrote

Reply to comment by H4wkeye47 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 pistons contract, too. The combustion will also act in the piston and piston rings pretty much evenly, tending to center the piston in the cylinder. The layer of oil the piston rings ride on in the cylinder cross-hatch will also mitigate wear, even at low temps. The main concern might be that the piston contracts more than the cylinder, so some additional fuel dilution and bypass may occur, requiring a more-frequent oil change in the winter.

Also, the longer the engine is maintains at reduced temperatures the more wear there will be. Idling to warm an engine up takes a lot longer than gently driving off. While driving at low loads, I would argue that you’re actually reducing wear compared to excessively idling to warm up all the time.

Practically speaking, driving off gently soon after starting the engine is the second best option. The first is an external source of heat, which is the point of the article, if I’m not mistaken.

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tkenben t1_iurg6qv wrote

I've read a few books on taking care of older cars, though I imagine the same holds for modern vehicles. They all say, all things being equal, it is better to put the engine under light load than to run it stand still to warm up.

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