Warming up your car before driving in cold weather can damage the engine (2016)

On most mornings my windows will fog on the side I just cleared before I can get the other side clear. I clean my windows, and then a couple miles down the road they clear up, otherwise it's will be a while before they are clear.

Having a water jacket around the cylinder makes it less possible for the cylinder to heat (and change size) unevenly versus an air(/oil)-cooled engine. That same water jacket permits the tolerances to be set to assume a maximum head temp under 300°F (versus 460°F for airplanes). That means the steel rings don’t have to deal with as much dissimilar expansion as the aluminum heads and pistons. This allows engineers to choose tolerances accordingly. It’s not so much modern metallurgy or electronic controls, but a factor of having a lower temperature range.

A two minute warm up is good for cars in winter, even with synthetic oil. Slow-ish speeds for a couple of miles will warm up the engine nicely. Keep in mind, when you start you vehicle on a cold morning, it high idles for a few minutes. This is by design.

Great and interesting replies as usual. For my two cents, don't trust the dealer where you bought your car. My wife and I bought a new Ram truck in 2021, I asked the salesmen what are the engine break-in best practices. He said he didn't know, no surprise there, so he called the service manager. The manager told him to tell me there is NO break-in required for these new "crate engines" these days!

I was shocked, so after I returned home I read the manual. It had concise instructions for breaking in both the engine and the transmission, which I was careful to do. There is plenty of stories on the web about the engine in my truck having upper engine problems, perhaps they believed the dealership.

ICEs will also use recycled exhaust to warm intake air. There's a separate sensor for intake air temp and I think a separate oxygen sensor that should inform the fuel mix.

At least in my performance car, there are separate gauges for engine oil, transmission fluid, coolant and air intake temperatures. Those are all exposed to me in dash.

I think traditionally, the only temperature exposed to the driver is the coolant temperature as that's usually the only one that really causes problems with overheating.

Once upon a time, before fuel injection and effective manifold heat, cars were not very drivable when cold.

The gasoline would not vaporize well in the cold carburetor so the “choke” had to be set to enrich the mixture.

When the vaporized fuel interfaces with cold metal in the intake manifold and intake passages in the head(s), the fuel condenses out of suspension, creating a very lean mixture, despite the choke being set. Combine this with dropping revs from leaving a stop in a manual transmission car, and stalls were frequent.

The solution was to allow the engine to “warm up”.

I have an old Toyota fj40 that reminds me of the before times when it’s cold.

The author of the article got many things wrong.

Washing the cylinders is a thing, but the cylinder has just had a combustion event in it that runs at 2600°F or higher. There is very little oil on the cylinder walls during the “power stroke” in a 4-cycle engine. The walls are reoiled on the exhaust, intake and compression strokes.

A study by the Society of Automotive Engineers (SAE) found that the temperature of the combustion chamber walls (the top section of the cylinder wall), specifically, ranges from 265° F under limited throttle to 475° F with the throttle wide open.

https://www.sae.org/publications/technical-papers/content/93....

The flashpoint for motor oils is 300-475° F, which is why you can maintain a thin film in the cylinder walls.

Excessive idling will foul spark plugs and valve seats.