@Gordon Nichols posted:That's not so different - It's acting just like mine on my T-1.
Maybe because it's easier for the coolers to keep you under 210F by opening the valve at 180F, than it is by waiting til you're at 200F and trying to quickly bring it back down?
There is probably some old French formulae from my ancient Thermo-Dynamics class that explains all that, but I most assuredly was asleep during that lecture. I just know that oil heats and cools faster than water (which is good for most of us).
I never took a thermodynamics class, but I deal in heat rejection for a living, and was curious about this statement (especially with Ray questioning it).
"Specific heat" is a value (the ratio is expressed as a single number) relating to the amount of heat (in calories) needed to raise the temperature of 1 gram of a substance by a 1° C as compared to the amount of heat needed to raise that of the same mass of water by the same amount. At 4° C, it takes 1 calorie to increase the temperature of 1 gram of water by 1°C. Therefore, the specific heat of water is very near "1" (depending on the temperature of the water in question).
Very few substances have specific heat values greater than water, which means that water can absorb a LOT of heat without skyrocketing in temperature. As an aside, the air in our atmosphere also has a specific heat value around 1, but this isn't the only consideration in a cooling medium.
Substances with lower specific heat values take less heat to raise the temperature by 1° C. Motor oil has different specific heat values at various temperatures (most substances do), but used motor oil at 100° C (212° F) has a specific heat of about .5, which means it takes half as much heat to raise the temperature by the same amount, and it absorbs and rejects heat 2x as fast as water (by weight).
This isn't the only consideration in heat transfer, but it is important. The density of the substance is also really important (which is why water does a better job than air as a coolant-- one has to move a LOT of air across a surface to pick up any meaningful amount of heat).
I suppose this means that oil is "better" than water as a coolant, if the heat being picked up has a way to be rejected (with a big enough oil cooler), and there's enough volume moving through the engine-- but as I said, there are other heat transfer considerations, and my brain is pretty full right now.
@IaM-Ray posted:funny most cars get water heat faster than the oil temp going up
I believe this is because the water temperature is more actively managed than the oil temperature in most engines, and that the coolant "warming up" is being recirculated through the heads and around the cylinders, and bypassing the radiator until it gets hot.
The oil in most engines doesn't circulate around the really hot parts very much at all.