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Comment by sandworm101 | Hacker News Reader

The difference is that people warm up their car for comfort, not necessity. At sub-zero temperatures a modern gasoline-burning car[1] doesn't need to warm up for more than a few seconds, at least once it is properly started. The only practical reason to let them warm up before moving is to get some heat into the passenger compartment.

[1] The issues regarding diesel in winter is a whole other discussion. Diesel fuel is longer molecules and gets very thick in cold. Diesel cars/trucks/generators can have real issues in winter.

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But enough people do it for comfort that my last two cars came with remote start as standard.

You're being too negative saying starting your car early is the same as taking care of a horse, which undermines your point - it makes you look anti-EV and less sincere.

> The only practical reason to let them warm up before moving is to get some heat into the passenger compartment.

Which can be pretty critical for safety - my breath fogs the windows if I don't let the engine warm up for at least a couple minutes before driving when it's -20C.

This makes no sense to me. I drive at or around those temps all the time. Sure today it was only -16C but it has been like that for forever now. Like the GP since about November. Some breaks with warmer weather, some stretches of -25C for weeks on end.

I have yet to have my breath fog up the window even if I start the car and drive off right away.

Of course it's cold. Of course the radio display is sloooooow. You can feel how much slower releasing the clutch is. Can't get into first gear at all unless the car is fully stopped either. So rolling stops need to use 2nd gear.

Make sure you don't use the washer fluid. Scrape everything free. Even with pure "-40" fluid you will get it to freeze and you will have to wait or use the wiper fluid constantly until things get warm. Have the blower on de-fog for the windshield and even if you don't wait even a second before driving off you should have no issues at all. Even the cold moving air is enough to keep things fog free. And defog actually runs the AC too, not that it's needed when the cold outside air you're blowing onto your windshield there has much need to be dehumidifierd.

Not sure what to tell you. I do all those, obviously, I live in a place where I also experienced -25 for couple weeks straight straight (and never anywhere close to -40). Agree on clutch and LCD, agree on not using washer fluid and scraping the windshield properly, and I'd add on lift your wiper blades now that the sun has some heat as your wipers will easily freeze on top of the mini-greenhouse that is your dash. But if I hop in my car and drive away immediately, the windshield will be foggy before I've gone a km - regardless whether I have the compressor (defog) on or not.

It is necessary to let my internal combustion van warm up for at least a minute on a cold day, otherwise the steering and brakes feel heavy to me. Plus, I don’t like to think of the damage being done to the engine cylinders if I drive without letting the oil warm up. And it takes many seconds just to start.

Either way, it is not my experience that you can drive a combusting car “seconds” after ignition.

This has not been necessary for quite some time. With modern tolerances in manufacturing, it is not necessary, even wasteful (burned gas and small amounts of wear that add up over time) to warm up a vehicle.

It may have been another story at long ago with larger gaps between rings, differential expansion of materials, newer oil formulations and so on.

With my daily driver 1995 Grand Prix (which just a few weeks ago bit the bullet, non-engine related), I never, even in the coldest weather let it sit idling warming up. Most mornings even around 0F, I turned the key and drove off. It died with ~289,800 miles. It did not consume any oil or coolant, the spark plugs are clean as new.

In fact, driving off easy will warm the engine up faster than letting it idle.

My partner’s 2017 Subaru asks us with an indicator to let it warm up on cold mornings.

Interesting, I have never seen such a thing. Perhaps it's more for comfort than mechanical reasons?

My Tesla auto warms up every morning on a schedule. If I didn't set the schedule it's literally a button tap on from my phone. That's a far cry from burdensome.

I warm up my Pete car for engine longevity.

That was a bigger thing in the past. Once upon a time engines were made with different metals that expanded/contracted at different rates. Then is was a good idea to let the engine get all up to the designed temp before putting any load on the engine. And carburetors were sensitive to temperature too. But modern engines with modern tolerances are all built out of one metal, mooting most of the reason behind letting the engine warm up completely. I wouldn't go racing on a cold engine, but running at 2000rpm driving slowly won't do more damage than idling at 1500rpm. Some even argue that doing so will get the engine up to temperature more quickly, reducing wear.

New engines are however made en masse out of alu which expands more than iron/steel. The argument that driving reduces wear makes little sense to me since whatever you do outside of sitting in neutral (fast idling if need be/not already programmed into the ECU) is increasing stress on the components that are not (optimally) lubricated and at a tighter than optimal clearance. Then again manufacturers know people can't even wait 30 seconds so engines are designed with that stress in mind so it's not the end of the world.

Most of the car manuals for the last few cars I've owned (VW Passat, Kia Rio) all state to avoid excessive idling in general. Cylinder wash from unburnt gas at idle as the car warms up being the main culprit in engine damage. It rarely gets below 20F or so here so at most I start the car and give it a few seconds to get oil moving and once I see the revs come down its careful sub 2.5K rpm driving as the car warms up.

Weren't the excessive idling warning introduced as an emissions thing? Correct me if I'm wrong. Just did a little search and found a nice compilation of user manual info regarding startup procedure [1] and they all pretty much go on about wasted fuel.

[1]https://info.ornl.gov/sites/publications/files/pub61263.pdf

Engines are lubricated almost immediately. The oil pump is typically camshaft driven, so it's only a matter of seconds before everything is lubricated. In addition, modern oils tend to "stick" to parts better and don't drain off as easily. It takes quite some time before they're completely dry.

As far as the material, at one time engines had components of various materials. Blocks of cast iron, heads or intake of aluminum. Now as you state, they are mostly aluminum. While it may expand more than steel, the majority of the components are going to expand at the same rate, unlike in the past.

Oils are definitely better but I really don't believe the marketing in winter. At low temperatures even modern oil has high viscosity. Combined with tight bearing clearances I firmly believe in waiting a bit to be sure everything is nicely coated. Maybe I'm just paranoid from horror stories of dudes getting on their bikes and ragging them right off the bat, seizing the engine.

I mentioned the aluminium mainly because piston slap came to mind. More slop, more slap. It's better than everything twisting though.

I use full synthetic engine oil for cold weather startability, primarily.

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