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doesnt mean the oil is fully warmed up...Right. So we should still take it a little easy,
Until we know the oil is fully flowing correctly...
Right???
Cyberbill
 

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The oil temp isn't going to be much different from the water temp. It's all inside the same engine.

Once the light goes out it's usually less than a minute until it's up to normal operating temperature. I don't think you need to worry too much about the difference. The oil is 5w-40, so its viscosity doesn't change much with temperature.
 

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The blue light is to advise of low coolant temp, is that what you mean? (i.e. it's not advising on oil temp?)
Is there anything we can buy that would tell us oil temp and intake air temp?.?
An Ultragauge or an Aeroforce Interceptor will be able to tell you coolant temp and IAT, but unfortunately not oil temp.
 

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doesnt mean the oil is fully warmed up...Right. So we should still take it a little easy,
Until we know the oil is fully flowing correctly...
Right???
Cyberbill
The oil is warmed up and at operating temperature before the coolant is. The only concern over oil at startup is whether it has gotten into all the bearings. It's temperature is of no real concern. Oil temperature concerns are after the engine has been running a long time under stress. Overheated oil can be an issue.
 

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The oil is warmed up and at operating temperature before the coolant is...
Incorrect. The thermal conductivity (W/m K) of water (and ethylene glycol) is higher than oil, which means water can absorb (and release) heat a lot faster than oil; that, and in an automotive application it's thermostatically controlled.

The general consensus is that it takes engine oil approximately 20 minutes to reach operating temperature.
 

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Incorrect. The thermal conductivity (W/m K) of water (and ethylene glycol) is higher than oil, which means water can absorb (and release) heat a lot faster than oil; that, and in an automotive application it's thermostatically controlled.

The general consensus is that it takes engine oil approximately 20 minutes to reach operating temperature.
Thermal conductivity is not the relevant property. Heat capacity is. It takes much more heat to raise the temperature of water than a similar amount of oil. There's also twice as much water as oil, so the water in general heats up much more slowly.

It's all in thermal equilibrium since they're circulating within close proximity in the same engine. Therefore, the oil temperature is held back by the more slowly heating water. By the time the water is hot, the oil is plenty hot.
 

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Nope

One might theoretically think so...but that is why theory usually needs to be backed up with demonstrative proof.

Coolant faster than oil.

www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=2573049

If you read through, aside from the last guy that won't give up, in most cases, and in the example shown about halfway through, your oil temp will trail your coolant because oil is only restricted when it is too thick (pressure bypass) while coolant is restricted by the thermostat to come up to operating temp faster.

You can check your self..... start your car up, drive around the block and change your oil. I bet you'll find it to be cooler than the surface temp of your radiator.

Your coolant will likely be warm in a few minutes while your oil will take 10-20 to come up to temp.

J


Thermal conductivity is not the relevant property. Heat capacity is. It takes much more heat to raise the temperature of water than a similar amount of oil. There's also twice as much water as oil, so the water in general heats up much more slowly.

It's all in thermal equilibrium since they're circulating within close proximity in the same engine. Therefore, the oil temperature is held back by the more slowly heating water. By the time the water is hot, the oil is plenty hot.
 

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Thermal conductivity is not the relevant property. Heat capacity is.
Heat capacity is only relevant insofar as to explain why water (even in an ethyl glycol mixture) is a better coolant than mineral oil...

It takes much more heat to raise the temperature of water than a similar amount of oil.
That is true, all else being equal (which is to say, in isolation).

There's also twice as much water as oil, so the water in general heats up much more slowly.
You've omitted the fact that a decent portion of that "twice as much water" is held within the radiator and associated hoses, the flow into which is thermostatically controlled.


It's all in thermal equilibrium since they're circulating within close proximity in the same engine. Therefore, the oil temperature is held back by the more slowly heating water. By the time the water is hot, the oil is plenty hot.
A cursory search confirms most disagree...

http://www.i-club.com/forums/aftermarket-forced-induction-turboed-factory-na-engines-62/what-heats-up-first-oil-coolant-1499/

https://bobistheoilguy.com/forums/ubbthreads.php/topics/2573049/1

https://forum.miata.net/vb/archive/index.php/t-103493.html
 

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Heat capacity is only relevant insofar as to explain why water (even in an ethyl glycol mixture) is a better coolant than mineral oil...



That is true, all else being equal (which is to say, in isolation).



You've omitted the fact that a decent portion of that "twice as much water" is held within the radiator and associated hoses, the flow into which is thermostatically controlled.




A cursory search confirms most disagree...

http://www.i-club.com/forums/aftermarket-forced-induction-turboed-factory-na-engines-62/what-heats-up-first-oil-coolant-1499/

https://bobistheoilguy.com/forums/ubbthreads.php/topics/2573049/1

https://forum.miata.net/vb/archive/index.php/t-103493.html
OK, I stand corrected on the temperature differences. Nonetheless, the thermal conductivity is irrelevant. The main difference seems to be that the coolant is thermostatted, while the oil isn't.

Beyond that, getting oil up to temperature is a largely archaic issue with modern multi-viscosity synthetic oil. The reason oil needed to be brought up to temperature previously was to get it thin enough pump easily and to flow well to all the nooks and crannies of the engine. 5W-40 has a viscosity that's almost independent of temperature, so it doesn't really matter that much what temperature it is.

So yes, there is a difference between the oil temperature and the water temperature, but it doesn't make any difference these days.
 

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Thermal conductivity is not the relevant property.
Tom is correct. The oil does not need to be hot. That is why a hybrid car can switch from electric drive to gasoline drive instantaneously without harm to the engine, even on really cold days.

Those of you who think the oil temperature needs to warmed up before heading out to work should let your engines idle in the garage for twenty minutes each morning.
 

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The engine itself is the most important temperature consideration, moving parts and their interaction with stationary parts. The best measure of that temperature is the coolant, assuming that measurement is taken from the engine block and the thermostat is working properly.
 

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The engine itself is the most important temperature consideration, moving parts and their interaction with stationary parts. The best measure of that temperature is the coolant, assuming that measurement is taken from the engine block and the thermostat is working properly.
Looking at this interesting thread from a layman's perspective, I guess that an engine's " full operating temp" measured in the coolant is one sign of it's efficient operation. By that time the cylinders have warmed enough to promote combustion and oil has thinned sufficiently to ease friction. When the blue light is on this efficiency is absent.
 

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Discussion Starter #16

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So I gues I'll keep it under 3,000 rpm until 15 to 20 minutes, and make sure I put a 1/2 quart of Lucus Full Synthetic oil treatment with each oil change, to be safe,..
Cyberbill
To be extra safe, keep it in the garage - heated - until outside temperature is 71.2 with a relative humidity of 56.666 (recurring). Then only drive it between the hours of 7 and 8pm...

Or just tape over the blue light and guess 'good enuf'.

Or, as we used to say, 'don't sweat the blue light.'
 
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Tom is correct. The oil does not need to be hot. That is why a hybrid car can switch from electric drive to gasoline drive instantaneously without harm to the engine, even on really cold days.

Those of you who think the oil temperature needs to warmed up before heading out to work should let your engines idle in the garage for twenty minutes each morning.
I see you've conveniently changed the topic; having both initally stated the oil came up to operating temperature before the coolant. Tom has accepted that, with the proviso that despite being incorrect it really doesn't matter. :confused:

Now you're adding to this by being patronising and instructing people to let their engines idle in the garage for 20 minutes before driving away. That is also wrong. It is well established that doing this does more harm than good.

From the country that knows cold weather; there's a reason they install block heaters and "drive with a light throttle until the oil is warm and lubricating well"...

http://thechronicleherald.ca/wheelsnews/1176824-starting-engines-in-cold-weather

As for the heat capacity of water versus oil, it is relevant, but not in the way either of you are suggesting. Some introductory physics for you...

http://www.introduction-to-physics.com/high-specific-heat-capacity-of-water.html

As for hybrid cars, we'll have to agree to disagree. The well established evidence does not support your claim.
 

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Tom is correct. The oil does not need to be hot. That is why a hybrid car can switch from electric drive to gasoline drive instantaneously without harm to the engine, even on really cold days.

Those of you who think the oil temperature needs to warmed up before heading out to work should let your engines idle in the garage for twenty minutes each morning.
For those not alert enough to get it, this is sarcasm.

I have been trying to stay on topic. Since the question related to whether the car was ready to run hard after the blue light went out, I responded that it was because the oil temperature did not need to be hot. When I used the phrase operating temperature, I meant it in the context of a temperature sufficient to operate at, not some maximum theoretical oil temperature. I never said the oil temperature was as high as the coolant temperature because that is irrelevant to the car being ready to run.
 
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