That sure was never my experience.
Oil temperatures.
- Thread starter iunderpressure
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What are you driving? Since you've got an oil temp gauge, it would tend to suggest some higher output potential engine ..perhaps of higher power density.
The oil temp is sustained by load. Once the combustion process is take out of the loop, it drops (within a given range) quite easily. You're "maintaining" it.
I doubt that you have a gauge on some bread and butter engine. An exchanger would certainly dampen changes in temp.
In a sensible sized sump in a non-exchanged engine it takes about 12-14 miles to peak out. The curve is very slow for the last half of the trip to that temp. You've done the "bulk" of the heating where the differential is most favorable for heat to migrate out through the oil. As you approach coolant temps, that thermal back pressure stops allowing AS MUCH heat to escape through the oil ..the coolant (which is regulated) starts dumping more of it through the radiator (and probably out the exhaust - maybe). At that 12-14 mile mark, you should be down to multiple seconds per degree ..at the terminal temp (whatever it is on this "steady state" trip) it will tick up VERY SLOWLY. That's where everything balances out.
Shut the valve on the heat supply and the temp should go away very quickly.
The oil temp is sustained by load. Once the combustion process is take out of the loop, it drops (within a given range) quite easily. You're "maintaining" it.
I doubt that you have a gauge on some bread and butter engine. An exchanger would certainly dampen changes in temp.
In a sensible sized sump in a non-exchanged engine it takes about 12-14 miles to peak out. The curve is very slow for the last half of the trip to that temp. You've done the "bulk" of the heating where the differential is most favorable for heat to migrate out through the oil. As you approach coolant temps, that thermal back pressure stops allowing AS MUCH heat to escape through the oil ..the coolant (which is regulated) starts dumping more of it through the radiator (and probably out the exhaust - maybe). At that 12-14 mile mark, you should be down to multiple seconds per degree ..at the terminal temp (whatever it is on this "steady state" trip) it will tick up VERY SLOWLY. That's where everything balances out.
Shut the valve on the heat supply and the temp should go away very quickly.
I don't have a car with a gauge; I am instead speaking about what I observed while driving many German cars with them. What I observed does not remotely resemble what you are saying.
With no oil cooler and a pan with a smooth exterior surface I'm not sure why the bulk oil temp would drop off that quickly either - unless you're in a cold ambient temp. The presence or not of underside engine coverings would be a consideration too.
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If you observe the upramp, you can easily see the slowing of temp gain. You're barely at an exchange advantage with your sustained output level. Just inching along on the up ticking in temp. Now remove the ONLY thing providing the thermal input with ALL the same rejection that barely allowed that upramp ..and it will crash.
I'm not talking dropping 30F ..but a 10F-15f drop is almost immediate (non-exchanged engine). Return to the same power mode and you will return to the same "one tick at a time" lazy increase in oil temp.
Just driving down the highway @ 60-70mph and letting off the gas for an offramp. That oil temp will retreat and it will take just as much time as the last mile or three to return to that "steady state" as it did on the initial upramp curve.
I'm not talking dropping 30F ..but a 10F-15f drop is almost immediate (non-exchanged engine). Return to the same power mode and you will return to the same "one tick at a time" lazy increase in oil temp.
Just driving down the highway @ 60-70mph and letting off the gas for an offramp. That oil temp will retreat and it will take just as much time as the last mile or three to return to that "steady state" as it did on the initial upramp curve.
Originally Posted By: Gary Allan
What are you driving? Since you've got an oil temp gauge, it would tend to suggest some higher output potential engine ..perhaps of higher power density.
The oil temp is sustained by load. Once the combustion process is take out of the loop, it drops (within a given range) quite easily. You're "maintaining" it.
I doubt that you have a gauge on some bread and butter engine. An exchanger would certainly dampen changes in temp.
In a sensible sized sump in a non-exchanged engine it takes about 12-14 miles to peak out. The curve is very slow for the last half of the trip to that temp. You've done the "bulk" of the heating where the differential is most favorable for heat to migrate out through the oil. As you approach coolant temps, that thermal back pressure stops allowing AS MUCH heat to escape through the oil ..the coolant (which is regulated) starts dumping more of it through the radiator (and probably out the exhaust - maybe). At that 12-14 mile mark, you should be down to multiple seconds per degree ..at the terminal temp (whatever it is on this "steady state" trip) it will tick up VERY SLOWLY. That's where everything balances out.
Shut the valve on the heat supply and the temp should go away very quickly.
I have an oil temp gauge on my work-a-day 5.4L Ford in an F-150HD and what Gary says is more or less what I see. My oil temps runs at or slightly above coolant temp in normal driving. I have owned the truck for two years now, and it's my farm truck. I haven't climbed any mountains with it yet, but thus far, it's only exceeded 212F once. It takes about 15 miles of steady driving to get the oil temp up to it's peak. I've not noted how fast it drops but I guess I will now
I have had oil temp gauges on other vehicles, one a Land Rover 2.25L four, which I worked the mucus out of for nearly 160K miles, and I saw 250 a couple of times (I ran 20W50 in it in those days). I once drove it coast to coast with everything I owned in, on or behind it and went nearly 3000 miles with my foot to the floor.
What are you driving? Since you've got an oil temp gauge, it would tend to suggest some higher output potential engine ..perhaps of higher power density.
The oil temp is sustained by load. Once the combustion process is take out of the loop, it drops (within a given range) quite easily. You're "maintaining" it.
I doubt that you have a gauge on some bread and butter engine. An exchanger would certainly dampen changes in temp.
In a sensible sized sump in a non-exchanged engine it takes about 12-14 miles to peak out. The curve is very slow for the last half of the trip to that temp. You've done the "bulk" of the heating where the differential is most favorable for heat to migrate out through the oil. As you approach coolant temps, that thermal back pressure stops allowing AS MUCH heat to escape through the oil ..the coolant (which is regulated) starts dumping more of it through the radiator (and probably out the exhaust - maybe). At that 12-14 mile mark, you should be down to multiple seconds per degree ..at the terminal temp (whatever it is on this "steady state" trip) it will tick up VERY SLOWLY. That's where everything balances out.
Shut the valve on the heat supply and the temp should go away very quickly.
I have an oil temp gauge on my work-a-day 5.4L Ford in an F-150HD and what Gary says is more or less what I see. My oil temps runs at or slightly above coolant temp in normal driving. I have owned the truck for two years now, and it's my farm truck. I haven't climbed any mountains with it yet, but thus far, it's only exceeded 212F once. It takes about 15 miles of steady driving to get the oil temp up to it's peak. I've not noted how fast it drops but I guess I will now
I have had oil temp gauges on other vehicles, one a Land Rover 2.25L four, which I worked the mucus out of for nearly 160K miles, and I saw 250 a couple of times (I ran 20W50 in it in those days). I once drove it coast to coast with everything I owned in, on or behind it and went nearly 3000 miles with my foot to the floor.
My work truck has a 13 liter Cat engine with a 34 liter ( 9 US gal ) sump. Oil temp is just over coolant temp normally. One of my runs takes me up a "hill" that's 6 miles of 6% grade followed by 6 more miles of 7%. Oil temp behaves just as Gary described. It takes most of the way to the top, almost 20 minutes at 100% load, to reach 250 deg, increasing more slowly as the temp rises. Once I crest the hill and the engine load drops to 0% it takes about one minute for the oil to cool back down to 200.
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Let me also add that in my experience with a bread and butter application that I reached a peak temp of around 220F+/- that rarely got breached. I speculate that it too created its own thermal back pressure (with all things in terms of thermal supply and rejection considered) reached a given temp where the coolant/radiator was the easier path to exit through. That (more or less) "fixed ceiling" on the coolant temp made it a more attractive egress point.
Now peak your cooling capacity beyond its reserve (like where one is ALLOWED in some Euro at sustained HIGH OUTPUT) ..and those equation exchanges are going to be altered ..which your view should too.
Qualifications (terms and conditions) ..the devil is always in the details.
Now peak your cooling capacity beyond its reserve (like where one is ALLOWED in some Euro at sustained HIGH OUTPUT) ..and those equation exchanges are going to be altered ..which your view should too.
Qualifications (terms and conditions) ..the devil is always in the details.
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