Oil Temperature

Heres something I've wondered about for awhile (especially this time of year with the deep-freeze going on here)
With a vehicle left exposed to the elements overnight, does the oil in
the crankcase only cool to the actual outside temperature, or does "wind chill" drive it lower?
Regards, Al.
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Wind Chill was invented by weather reporters to make their reporting more exciting. It is what the temperature feels like on your skin and has nothing to do with the real temperature of inanimate objects. Your oil will only drop to the real temperature.

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A simple way to prove or disprove if wind chill actually changes temperature is to place a fan in a closed room. Put a thermometer a few feet in front of the fan. Allow the thermometer to have enough time to adjust itself to the temp of the room. Turn on the fan and watch to see if the thermometer changes its reading.
-- Mike.................................................... "Opportunities are spawned from crisis"

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Wind chill affects how quickly something can be cooled.
Assume a zero-degree day. A heated body will lose heat at a fixed rate.
but If it's zero, and there's a 20 mph wind, then heat will be lost at a faster rate.
Either way, body temp can't drop below 0 degrees.
wrote:

<rj>
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This is EVAPORATION related only, the wind as no effect on (dry) object.
A dry peace of metal wont go below ambient temp wind or not, but if you put humidity on it (water and such volatile liquid), now the temp will drop.

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| This is EVAPORATION related only, the wind as no effect on (dry) object. | | A dry peace of metal wont go below ambient temp wind or not, but if you put | humidity on it (water and such volatile liquid), now the temp will drop. |
Your statement is true if the humidity levels are below 100%. However, if the atmosphere is at 100% humidity, evaporation cannot occur and therefore the cooling effect of evaporation can't happen. The lower the humidity, the quicker evaporation rate and the greater the cooling effect (until the water is gone, naturally).
There is another caveat to add to this dynamic as well..."traditional cooling". It's the opposite of traditional heating. On a crystal clear cloudless night, objects do typically drop a few degrees below ambient air temperature due to the retained heat within those objects being "radiated" from the surface of the objects and out directly into space. That is how frost _can_ occasionally form on the surface of a car when ambient air temperatures are 33-36 degrees (sometimes as high as 40 degrees) and when the wind is very light.
Heat _flows_ from warmest to coolest and always attempts to achieve a equilibrium. At night, objects on the surface of the earth are relatively warm compared to the temperature in space. Without clouds (especially), some of this retained heat energy radiates out into space from the objects (like your car). The cooling of these objects actually contributes significantly to the cooling of the air itself.
The opposite, of course, is traditional heating where a object can be heated above ambient temperature by a distant heat source (e.g. radiator, fireplace/campfire, the sun). We are all familiar with that.
But, having said that, the difference is small...only a few degrees. And, as pointed out earlier, wind by itself will _not_ make the object cooler (or warmer for that matter) than the ambient air temperature. Actually, wind helps keep the object closer to ambient air temperature. When an object is impacted by traditional cooling, wind warms the object up a degree or two closer to ambient (but never above ambient). When the object contains a heat source (or is heated by radiant solar energy), the wind cools it down a degree or two closer to ambient (but never below ambient).
Clear as mud, right?! :-)
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My spell-check changed the term "radiational cooling" to "traditional cooling". Thought I caught it before it sent...guess not!
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The wind-chill factor was developed for the human feel of temperature. This dose not affect engines or oils. If you put a thermometer into the oil, it would reflect the actual ambient temperature.
Yes, if there is wind, your engine will cool-down faster. But that is not what your weatherman means about wind-chill. "Wind-chill", is what a human will feel once the wind blows across your skin. Normal body temperature is 98.6 deg. On a cool Spring day (73 deg.), you would feel OK outside, with pants and long sleeves. If there is wind present, it will blow the heat off of you like a radiator fan. If the wind is strong enough, it can overcome your body's ability to compensate. "That", would be hypothermia. Spring days don't produce such winds in North America. This was just a hypothetical situation.
Your weatherman's claim of wind-chill, has nothing to do with cars. It's just the human feel of the cold.
Yes, one could figure out wind-chill factors for an engine being cooled down after running. But why? An engine has a thermostat, a control device that humans don't have. That thermostat will not allow the temp. of the engine to get lower than about 195 deg., when it is running. When you start your engine on a -7 deg. day, the engine and oil will be -7 deg.
GMdude
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