Condensation
MT - What Is the Optimum Engine Oil Temperature?
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Condensation
This thing made a liar of me. It touched 220* today on the highway. I don’t ever remember this but it’s not even hot out yet. My memory must be shot.
AZjeff
$50 Site Donor 2023
From? Combustion blowby as noted plus modern PCV puts air from the upstream intake into a valve cover and pulls it out of the other valve cover into the intake valves. Does that leave moisture in the crankcase?
bingo we got a winner here. Nice write up.
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Post is an excellent candidate for a "sticky." @dnewton3
Sometimes, we need technical but non-ultra-technical explanations.. not all of us are Steven Hawking levels of genius (yes, I'm saying that some here may in fact "over-enjoy" talking in terms so techncial, only they and 5 other people can understand. Your post was a great example of being technical without needing Gary Kasparov chess-playing ability to understand.)
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Just the heating and cooling of the engine will produce condensation. But it should burn off of any well designed engine that is allowed to reach the normal operating temperature of said engine.
FWIW, the displayed oil temp of my ‘02 Jaguar XKR (supercharged 4.0 L V-8) is almost always 16-20 degrees F higher than the coolant temperature. Giving the car an oil temp in the 205-220 most of the time. But I have seen it up to 240 in the Texas heat in stop and go traffic (using Mobil 1 0w-40 or 5w-40)
As mentioned already, the oil temperature in the sump / oil pan is going to be cooler than it is between the bearing surfaces and the moving engines parts.
Z
Out here in the dead of Summer it can hit 120+ F. Most of the time when it gets that hot the relative humidity is in the single digits. (4% to 8%).
If you spray water from a hose on the concrete, (which is no doubt much hotter), it's unbelievable how fast it will evaporate. You can literally watch it.
So I can't imagine moisture remaining in an engine for long when the oil gets up to 200 F. Or even 150 F. And the engine block on a modern vehicle isn't a pressurized boiler. There are all sorts of ways for that moisture to escape.
If you spray water from a hose on the concrete, (which is no doubt much hotter), it's unbelievable how fast it will evaporate. You can literally watch it.
So I can't imagine moisture remaining in an engine for long when the oil gets up to 200 F. Or even 150 F. And the engine block on a modern vehicle isn't a pressurized boiler. There are all sorts of ways for that moisture to escape.
OVERKILL
$100 Site Donor 2021
220 to 240 is good
twouvakind
Site Donor 2024
It's a car, not a lab. I for one see my oil temperature begin to register on my display at 124 degrees fahrenheit and then go as high as 223. I doubt auto manufacturers are that concerned with precision gauges. Speedometer indicated speed variants are a good example. On the other hand, police speedometers are sometimes "calibrated". YMMV.
Oil temps will generally follow coolant temps but take longer to reach the same temp.
With the engine working hard, I have seen oil temps reach 20-40 deg higher than the coolant temps.
I've only watched oil temps on 3 vehicles I've owned, but the results have been similiar.
Now a turbo or twin turbo engine really working hard, might see higher temps but can't say for certain.
With the engine working hard, I have seen oil temps reach 20-40 deg higher than the coolant temps.
I've only watched oil temps on 3 vehicles I've owned, but the results have been similiar.
Now a turbo or twin turbo engine really working hard, might see higher temps but can't say for certain.
Overkill, I have a 2016 Ram 3500/w Cummins. it has a oil temp and pressure display. But the interesting thing is those temps on the gages are calculated, not actual.
If I take my scanner, connect to the OBD2 port I have access to about 320 engine parameters, but the only reading regarding oil values is Oil Press Switch state open or closed. In other words, it has oil pressure or it doesn't. I've looked all over that engine and it only has one 2 wired oil pressure switch in the main oil rifle. I'm pretty sure the Hemi is the same way..
OVERKILL
$100 Site Donor 2021
I was actually over this with somebody before
Also, I have access to an actual Mopar WiTech pod, which gives access to everything, including the ability to perform updates.I'm not surprised the Cummins-equipped trucks "fake it" for some of the parameters.
The HEMI does in fact have real oil pressure sensors and oil temperature sensors, it's integral to the MDS system, that's how it determines if you've significantly deviated from spec visc or not, as it infers viscosity from oil temperature and pressure.
- The pressure sensor is a 3-wire unit on the front of the engine at the top of the timing cover, part #68334877AA
- The temperature sensor is above the oil cooler (on vehicles so equipped), per this diagram posted by The Critic:
I like 210-230°F for oil temp so glad to see that's verified. With a quality oil, I don't worry about oil temp until it starts to exceed ~260°F. I know some engines that cruise on the highway at 250-260°F oil temp. Once it gets above 260°F, then I want the best quality base oils available with an add pack that's happy in that heat range.
Remember, hot oil protects better. You have better additive reactivity and the oil stays cleaner.
Combustion by-products and condensation. Gasoline produces water as a by-product of combustion. Burning 1 gallon of gasoline produces 1.033 gallons of water. (C8H18 + O2 = CO2 + H2O) Most of that water exists out the exhaust as a vapor. Some of that vapor collects in the exhaust when you shut the engine off and can condense back down to liquid. That's the water you'll sometimes see dripping from the tailpipes on a cold start. Some of that water vapor inevitably finds its way past the rings into the crankcase and into the oil. Condensation also introduces water to the oil as the difference in temperature inside and outside of the crankcase causes the block to "sweat" and thus moisture enters the crankcase and the oil.
Remember, hot oil protects better. You have better additive reactivity and the oil stays cleaner.
Combustion by-products and condensation. Gasoline produces water as a by-product of combustion. Burning 1 gallon of gasoline produces 1.033 gallons of water. (C8H18 + O2 = CO2 + H2O) Most of that water exists out the exhaust as a vapor. Some of that vapor collects in the exhaust when you shut the engine off and can condense back down to liquid. That's the water you'll sometimes see dripping from the tailpipes on a cold start. Some of that water vapor inevitably finds its way past the rings into the crankcase and into the oil. Condensation also introduces water to the oil as the difference in temperature inside and outside of the crankcase causes the block to "sweat" and thus moisture enters the crankcase and the oil.
cool... as far as I can tell the Cummins models don't have a real oil press or temp sensor.. just a switch.. did not know that about the Hemi, but its a good thing.. I know mine is a liar... Give you a perfect example, you can be driving and the oil temp reading migh tbe 200 or so, but descend a large hill with the engine brake on and see the oil temp drop suddenly by 40 degrees.. logic decrees liquid temperatures dont change in an exponential manner in seconds.I was actually over this with somebody before
I'm not surprised the Cummins-equipped trucks "fake it" for some of the parameters.
The HEMI does in fact have real oil pressure sensors and oil temperature sensors, it's integral to the MDS system, that's how it determines if you've significantly deviated from spec visc or not, as it infers viscosity from oil temperature and pressure.
- The pressure sensor is a 3-wire unit on the front of the engine at the top of the timing cover, part #68334877AA
- The temperature sensor is above the oil cooler (on vehicles so equipped), per this diagram posted by The Critic:
OVERKILL
$100 Site Donor 2021
Apparently, if you had a HEMI, it would be part #5149077AB, but I'm not seeing one listed for the Cummins, so I suspect your suspicion is bang-on.
yeah, I have the actual Cummins part book,instead of the OEM parts list and it just lists a switch.. so that is how Cummins Inc sent engine to Mopar for final assembly. I used to have access to Cummins Quickserve, used engine serial number and CPL # to print myself a parts book for the engine.. beauty of Cummins is even thought they ship the engine to Mopar and Mopar warrants the stuff, you can buy parts direct at any authorized Cummins Distributor. all you need to know is the serial number of the engine and you save some money, mopar marking the parts up from Cumminsprices.
In order for any water vapor trapped inside the engine to condense, the dew-point of the water vapor relative humidity would have to be obtained for the inside of the engine to "sweat". Modern engines are essentially sealed from the ATM when shut-off due to a properly working PCV system, so it would be basically impossible for outside water vapor to ingress into an shut-off engine. However, the PCV system does pull ATM air through the engine to evacuate the sump, so in hot and humid environments, at shut-down the engine will be filled with more water vapor in a high humidity area vs a low humidity area.
If the engine was short tripped a lot (especially in cold winter climate), then there will me more trapped water and vapor inside the engine at shut-down. Driving a while (and even longer is cold winter climates) after the engine is at fully operational temperature helps keep the inside of the sump and "dry" as possible, and also allows the PCV system to properly evacuate any accumulated water condensation/vapor.
I get a kick out of the guys who disable the PCV system on their cars and put open to ATM breathers on their valve covers. That's the last think you want to do in order to keep water vapor and condensation out of the engine.
don't forget that blow-by gasses are filled with steam
Moisture leaves the engine via the PCV system.
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