[MadScott]

Oil pressure seems to be left out of the conversation - oil-starved journal bearings can be bad news if loaded immediately. SOP in piston-engine aircraft is to get the oil temperature and pressure "in the green" before doing run-ups.

There's a pretty good description here: https://www.machinerylubrication.com/Read/779/journal-bearin...

[dghlsakjg]

Piston Engine aircraft are probably not the right example to use.

They are almost exclusively air/oil-cooled, low-rpm engines, and a majority of them have designs dating back 50+ years.

[ledauphin]

sure, but the basic physics at the very heart of the issue (use oil to avoid direct contact between metal pieces) is exactly the same.

it seems very unlikely that modern refinements have completely reversed the concerns.

[sokoloff]

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.

[webnrrd2k]

I don't see how water jackets, pistons rings, and their tolerances are directly relevant here. The topic was bearings, and their lubrication and wear, in the larger context of warming up your car before driving in cold weather.

[sokoloff]

Imagine a cold-soaked engine with an aluminum piston, steel rings, a cast iron sleeve in an aluminum head. The aluminum piston will heat very quickly compared to the cast iron sleeve in an air-cooled engine. (There’s a massive aluminum heat sink in the form of the cylinder head.)

For a water cooled engine, there is a water passage around 3/16” from the cylinder wall which helps to bring the cylinder up to an even temperature more quickly and prevents a high heat flux from expanding the piston to the point where it can scuff the walls.

It’s not only oil pressure that is a concern for a cold-start to operating temps.

[bombcar]

Some vehicles have oil heaters to get the oil to operating temperature before even cranking.

These engines are often large enough to park a car inside, however.

[willis936]

My 2018 car (gasoline, turbocharged, direct injection) has coolant and oil temp readouts. The increase in coolant temp from a cold start leads the oil temp by a few minutes (exact time is dependent on ambient temperature and load profile).

Once the oil temp starts to get above 150F it very quickly gets to the operating temp (220F), so I view that as the point that it's okay to go above 3000 RPM.

If there are oil heaters then they must be far away from the oil reservoir temperature sensor and only have a local effect. As you say, that sounds like a feature for very large engines. It's probably a good practice to be gentle to car engines with cold oil.

[winrid]

Street cars have been using coolant/oil heat exchangers to bring oil up to temp faster and regulate its temperature under load since at least 1999 (source: VW's 1.8T, AEB and AWP motors).

https://store.ngpracing.com/acm-oil-cooler-heat-exchanger-1-...

[bluedino]

Most engines will have a lower redline until the engine has reached a certain temp

[bluedino]

Engine block heaters and oil pan heaters are the norm in the north. Plugs into an electrical outlet.

[upsidesinclude]

The most common heater of an industrial engine is for the jacket water. Keeping the entire block heat soaked is the easiest/safest way to heat the oil as well. Using a "prelube pump", which is a low pressure, low volume circulation pump that parallels the main engine driven pump, oil is continuously sent throughout the internal passages

[gonzo]

Unlikely to be starved, (unless it’s really cold and then you barely have any oil), but bearings can be washed out by high oil pressure, which is a consideration with cold oil.

[Gordonjcp]

If your engine doesn't have oil pressure before it's even finished starting, either it's a bit faulty or you're using a grossly incorrect grade of oil.