Coolant vs. oil

That’s a good point. I didn’t consider the temperature of the coolant in the engine. I was thinking of the coolant in the radiator.

252525, if you keep your car in good shape and maintain your cooling and lubrication systems by monitoring and changing the fluids and filter when you should, it’ll easily tolerate stop & go driving.

I think it’s imprtant too to understand that each engine design and cooling system design has a temperature “profile”. All the lubricant in your lubrication system is not at the same temmperature, and all the coolant in your cooling system is not at the same temperature. And they heat up differently and create different “profiles” depending on the engine’s conditions and depending on the engine’s operating environment. A system “profile” is going to be different at 30F ambient than at 80F ambient, it’ll be different at 70 mph than at 30mph, and an inline 4 will be different than a V6.

In short, we’re debating this as if it’s a static condition consistant across engine types. It isn’t. It’s a highly varying and dymic (constantly changing) “proofile” rather than a number. Even the number we see on the gage is just one point in the overall system.

The answer to this question is pretty simple, at least to us Subaru guys LOL. Reason being, we know that you shouldn’t get into boost in our turbo boxer engines until the oil is up to temp. The oil always takes longer to get up to operating temp than coolant does. Not sure if that’s because of the thermostat, or why. But I can tell you without a doubt that no matter what the outside temperature is- your oil always takes longer to heat up than coolant. I can start my car cold when it’s 80 degrees or 0 degrees and the coolant always comes up to temp well before the oil, and I always have to wait a few miles under load for the oil to come up to temp or at least to 180 or so before I will ever dip into boost. Hope this helps.

It depends on where the oil temperature is measured. Coolant constantly circulates since its purpose is to cool, so its temperature is mostly uniform. Coolant begins to heat up just a few seconds after starting since it circulates very close to the combustion chamber, which is where the heat originates from.

It takes a while for oil to be pumped out of the sump and make its way back down to the sump. The oil in the sump doesn’t heat up at all until warm returning oil drips back down to the sump. And that oil won’t be warm until the bearing surfaces that it came out of start to warm up from friction.

The XV10 Toyota Camry has an oil cooler on the engine that uses coolant. I suppose it acts as an oil heater shortly after the engine is started. Maybe turbo boxer Subarus should have this?