oil temps in oil pan

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I changed my oil last week after driving for about 45 minutes, so it had reached operating temperature for a good while. The oil temp gauge read about 190 degree F. The ambient temperature was about 55 degree. When I got home, I drove the car up on ramps, and because I was in a hurry, I decided not to wait 30 minutes before draing the oil. What's a slight risk of getting scalded, right? Naturally, I dropped the drain plug in the drain pan, which is the cheap kind. I had to go fishing for the drain plug, and to my great surprise, the oil wasn't all that hot. I could easily stick my examination-gloved (!!!) hand in there for 10 seconds without burning myself. I don't think the oil was hotter than 160 degree or so. I'm not sure where the gauge gets its data, but I guess it's at the oil pressure switch. I wonder if the oil in the pan ever gets hot enough to boil off condesation.
 
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I'm not sure you need to boil off condensation. Maybe 160F for a sustained period would cause evaporation. [I dont know] The oil is also flowing over much hotter engine parts in a thinner film, plus the friction of the flow itself.
 
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quote:
Originally posted by haley10: I'm not sure you need to boil off condensation. Maybe 160F for a sustained period would cause evaporation. [I dont know] The oil is also flowing over much hotter engine parts in a thinner film, plus the friction of the flow itself.
In the 1960s I had a couple of cars with 292 and 312 cubic inch Ford V8s. Both had oil temperature gauges. One ran at about 160F oil temp, the other at 180F. Both used the same oil. The oil in the 180F oil temp engine didn't generate as much sludge. Hardly a scientific test, but it fits the conventional wisdom that about 190F is a good sump temperature.
 

MolaKule

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moribundman

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Thanks for the links, Molakule. The relatively low oil temps in the pan make probably sense, because I hadn't been really racing the car or anything, but I had been cruising through town. I know that the oil temp gauge can show 250 degrees after prolonged high speed (>6000 RPM for an hour) driving.
 
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N. Florida, USA
quote:
Originally posted by haley10: I'm not sure you need to boil off condensation. Maybe 160F for a sustained period would cause evaporation. [I dont know] The oil is also flowing over much hotter engine parts in a thinner film, plus the friction of the flow itself.
I dont think water below a bunch of oil in a pan can evaporate, it has no access to air air to cary it away, same problem in a fuel tank, but I am sure that the bottom of the piston, the rings and bearings give enough heat to boil off any minor water present in the oil from consensation as it is circulated,
 

MolaKule

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Well, that's what the PCV system is all about; creating a weak vacuum with just enough flow to suck out vapors, including water vapors.
 
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MICH
I am currently using a separator inline on the PCV in my DAKOTA.Guess what I empty about 4 ozs of water muck every week.Since I installed the unit my intake stay cleaner,you got to remmmember that most of your idle air is induced through your PCV & a small ammount from your idle air valve,as long as your trottle plates are closed thats what yo'll get.
 

Al

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Elizabethtown, Pa
quote:
Originally posted by RavenTai: [QUOTE] I dont think water below a bunch of oil in a pan can evaporate, it has no access to air air to cary it away, same problem in a fuel tank, but
That' probably not an accurate model of whats hapening. The amount of sloshing in a pan with the agitation/high turnover rate will not allow oil to settle at all except when the car sits. [Smile] Hopefully as the links that Molakule posted-steady state temperature of oil may be belowcoolant temp in low loads and colder weather. But it is likely that oil temp most of the time will be at coolant temp and above. As load and ambient temperatures increase-oil temperature can run 300F or higher. SAE Technical Paper 2001-01-1073
 
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If the temp is over 212F, the water is going to boil anyway, BUT, as is indicated above, that water won't be sitting at the bottom of the pan, not with an oil pump pulling from the bottom of the pan. The temp does not even have to be above boiling though. Set a glass of water on a hot plate, keep the temp at 160F. The water won't be there all that long...
 

moribundman

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23,591
quote:
If the temp is over 212F, the water is going to boil anyway, BUT, as is indicated above, that water won't be sitting at the bottom of the pan, not with an oil pump pulling from the bottom of the pan. The temp does not even have to be above boiling though. Set a glass of water on a hot plate, keep the temp at 160F. The water won't be there all that long...
Coolant will not boil at 212 degree F or a little above due to being under pressure, which raises the boiling point. In your experiment, put a loose-fitting lid on the glass. [Wink] Actually, I'm not sure if there even is a problem with condensation in an oil pan, presumimg the car is driven regularly until the engine has been running with operatimg temperature for some time. I've never seen water come out when draining the oil, but maybe small amounts can become emulsified?
 
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quote:
Originally posted by MolaKule: Well, that's what the PCV system is all about; creating a weak vacuum with just enough flow to suck out vapors, including water vapors.
Another reason I may do a uoa. A malfunction in this overall system can cause bad things to happen. I'll also look for the GM manifold/throttle body leak. Neither is good for oil or engine. [ February 07, 2004, 02:16 PM: Message edited by: haley10 ]
 

moribundman

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quote:
Actually, put a tight fitting lid and a forced purge(AKA PCV) on it [Smile]
Hmm, my breather hoses go from the valve covers to the plenum/intake. They do not got from the sump to the intake. I'm not sure how much suction there is from underneath the valve covers down into the oil pan. [Wink] BTW, my car does not have a PCV valve. [Cool]
 
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May not have a PCV valve, but if it's a modern engine, it has some sort of PCV system. Keep in mind that water vapor expands quite a bit. Even if there were not very much flow from the crankcase to the upper engine via the breather system(and ther is in my V8), the water vapor would be expanding and be sucked out via the PCV system. That is exactly what it is there for, remove water vapor, as well as other combustion byproducts.
 
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Cleveland, Ohio
I have several Autometer gauges in my one car including a pair of electric temp units, one for the water and the other for the engine oil. The water temp sending unit is in the stock factory location. The oil temp sending unit is down low in the side of the oil pan. What I have observed is that it takes awhile for the oil to get up to temp. Once it does, it usually stabilizes at about 5 degree F higher than the water temp. This is most likely due to the factory water/oil preheater/cooler unit. One other thing I have noticed is that with a heavier viscosity oil, the temp changes are slower than with a lighter viscosity grade. I try to avoid short trips in this car. In fact if I have to go run a short errand in this car, I will typically drive a long loop just to make sure the oil get up to temp before she gets parked.
 
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