What temp does oil need to reach / maintain ?

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Where is the optimal temp range for engine oil? With something like a 5w20 oil, I'm guessing there is a temp range where it is most efficient and is hot enough to remove contaminants. I'm asking this in regards to engine operating temperature. Different vehicles use different thermostats and engine cooling setups. In particular, my truck came from the factory with a 203deg thermostat. That has been replaced with a 190 deg thermostat. Along with the thermostat change, I have changed the cooling fan settings for turn on. Since there should be relation to operating temperature and engine oil temperature, I'm just curious to see where this all falls together. Before people starting arguing about lowering your thermostat temperature, I'll just say that with these engines, many, many, many people are running 180 deg thermostats and revised cooling fan settings without any know problems. I felt better with going in between the factory temp and the lower 180deg that are the most popular. Since there has been some talk about computer systems running richer with 180 deg thermostats, and an occasional code for slow warm up, I felt the 190 is a good compromise. Lowers the engine temp about 14 deg, without bringing it down a total of 24deg as some others are doing. As we speak, the engine comes up to 190deg, thermostat opens, temperature drops down to 182 or so, and repeats the cycle while driving as it should. Cooling fans are set at 199deg to turn on, and only make it to that point while sitting in traffic, or stop light, etc. While driving, the natural air flow keeps the engine running without the use of cooling fans. So, that all being said, my engine oil does not reach 200deg + temps, and I'm wondering if 180-190deg temp's are enough to burn off contaminants etc.
 
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I believe so as long as its for an extended period of time at that temp. I would think 20 to 30 minutes at full temp would be good.
 
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Yeah I agree. Get it out and above 65mph for a bit would do. Idle at stoplights increases. If in doubt check your filler cap. If its got hot vapors then I assume you made it. Regular drives and operation should keep everything going. If all else fails perform a UOA and see what the mad scientist thinks.
 
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do you have an oil temp gauge? oil temp is not coolant temp. for that matter bulk oil pan temps are different vs the oil temp while its lubricating the engine. my 2015 forester usually has the oil temp at 205-218f but where that's measured... not sure. it has never gone below 210 while running/moving after its fully warm. I did see 207 after 4min at a long light.
 
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Sep 24, 2012
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Originally Posted By: Rand
do you have an oil temp gauge? oil temp is not coolant temp.
+1 What does swapping out the theromostat to a 190 degree thermostat do for you? Besides the obvious. Not questioning you, just curious.
 
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My Caprice, on 3.2cst (HTHS) oil, after 25km has an oil temperature (thermocouple in the oil at the full/add portion) of 105C --- 220F, quite a bit hotter than the thermostatically controlled coolant temperature. Sump metal temperature of 90C indicates that the oil raining out of the crank journals is quite a bit hotter than bulk oil.
 
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Water evaporates at 100 degrees so (to my reasoning) you would need to maintain that temperature for long enough to evaporate whatever volume of h2o is present.
 
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Having watched a vacuum dehydrator in action, and with a couple of sumps full per minute being thrown out the crank bearings at highway speeds, the 20 odd minute recommendation once heat soaked seems sound.
 
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I'm also curious, your lower thermo doesn't keep your CPU on closed loop? My understanding is about 180F is the temp suggested to remove moisture form your crankcase. My F-150 I have a oil temp and coolant temp gauge. Oil is much slower to come up to operating temp (my thermo is 192) than coolant. My coolant is the Prestone (I mix 60/40 distilled) yellow/green. Temp for mine, depends upon conditions and outside ambient temps. 5-20 M1 90F highway for 25 or more miles and mine will sit around 198-205F but 60F it's more like mid 190's and cooler temps have a more pronounced affect pushing it more toward 192.
 
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Wildly platform specific. Some cars and trucks respond extremely well to a small recalibration of the fans and a lower temp stat. My car gets huge gains in timing which translates to better throttle response and great economy, too. First, you do not need to get oil to 212 F to remove water. Evaporation is greatly accelerated even at 160 degrees or less. DURATION at temp is important, hence why short trips/colder climates require a hotter stat. Oil temps typically trend higher than water temp but take longer to get there, but if you have an oil cooler then they usually stay close. I would bet that on the highway or even good urban traffic the oil exceeds 200 degrees...
 
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Your truck came with a 203* thermostat for a reason. Changing it to a 190* thermostat might do more harm than good. Why did you change the thermostat and the fan settings? Keep in mind winter is coming and with the modifications you made your could take even longer to come to optimal operating temps, or worse it may never come to optimal operating temps now.
 
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I've contemplated adding a hotter thermostat on my truck, as it will only run at 190 or more if it is sunny outside (if it's 50 or less it seems to hang in the low 180's). Watching the SGII seems to indicate worse mpg's in the 180's, but perhaps that is my imagination. I think this year I will finally start blocking off the radiator for faster heating. Dumb question, but where are you measuring oil temp? I'd think the oil is going to spike in temp anyplace outside of the sump, which is where it may have the max surface area and most likely to dry out (if it had water in it). Oil sitting in a pocket on the head is likely much hotter than in the sump; perhaps that doesn't matter, as the pump will draw from the cooler oil.
 
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My t-stat is 180F, I have an oil filter mounted coolant/oil heat exchanger on it. This brings the oil up to temp faster and once the oil gets above coolant temp tends to mitigate the temperature. But the oil runs maybe 10F over coolant temp while under light load highway driving. A bit higher when the load increases.
 
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Originally Posted By: Olas
Water evaporates at 100 degrees so (to my reasoning) you would need to maintain that temperature for long enough to evaporate whatever volume of h2o is present.
Water evaporates whether it's 100c or -30c. Water boils at 100c iirc however that doesn't mean water won't evaporate at much cooler temps. I've seen ice cube trays go empty(took over a year) when left in the freezer,frozen solid. So if water only evaporates at 100c please explain freeze drying techniques and how they are able to dry things using cold. I'm not actually expecting an answer.
 
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What about fuel dilution vis-a-vis oil temp - - as in gasoline direct injection? Any theories/data about oil temp necessary and duration to drive off fuel dilution?
 
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Originally Posted By: m6pwr
What about fuel dilution vis-a-vis oil temp - - as in gasoline direct injection? Any theories/data about oil temp necessary and duration to drive off fuel dilution?
That is vehicle specific. My turbo will never drive off all the fuel and it is the main reason to change the oil (so they tell me) when I get it tested.
 
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Originally Posted By: m6pwr
What about fuel dilution vis-a-vis oil temp - - as in gasoline direct injection? Any theories/data about oil temp necessary and duration to drive off fuel dilution?
Since fuel evaporates at even lower temps than water the answer is it is easy to drive it out of the oil. The problem is tuning. I own a car with a factory spec of synthetic oil and a recommended interval of only 3000 miles. This is due to tuning that uses a lot of fuel. Most any higher performance engine does the same. Fuel dilution is not as harmful as people think, either...
 
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Hi, Johnny248 - Yes there is a desirable equilibrium between coolant and oil temperature. This is typically resolved at design level and then refined according to application IME the designer will aim for a bulk oil temperature (BOT) in the 80C-100C range. Typically this is around 85C and some engines have a "power down" actuation feature when the BOT reaches around 115C-120C Of course hot spots exist - the turbocharger is one that typically reaches >450V
 
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