What are safe oil temperatures during spirited driving?

So you are tagging me for a belief, but you've presented simply an alternate belief with nothing more than a web discussion as support.

Somewhat legendary for that but to address your point with an actual answer

You have to study pretty hard to find an exception, which may be out there. But I believe it is still accurate in saying "Thicker" vs. "Thinner" if I put it in terms of density.
Until then, I'm convinced that in general, an SAE 20 weight will cool more efficiently, especially when an oil cooler is involved, than 30, 40, or 50 weight oils.

For general conversation, that's close but not exactly right.

Lets say "heat removal" rather than cooling because that cycle is a 3 part triangle where the heat capacity of the "coolant" ( regardless of what it is really) is 1 part but that 1 part is constricted by the other 2.

So for discussion sake, lets take the "oil" out and substitute chemical X and lets say "X" has a heat capacity of .99 ( out of 1)

Step 2 is "volume and velocity" times the surface area. ( how much of "X" in terms of volume touch the surface of the heat to be removed and how long it sits there)- there's a limit to this because heat capacity is hard stopped by change of state of chemical "X" ( has to stay between)

Step-3 is removing the heat from "X" so it can go back and absorb more and continue the cycle.

Imagine this scenario- you have 3 steel plates ( say 6x6x1") heated bright cherry induction so they are through heated evenly

All for 10 minutes and with only 5 gallons

You squirt water on one side (covering the side fully) and it drains in a bucket

You have a bucket and do the lift/immerse for 10 seconds cycle

You drop it in the bucket and let it sit

That's 3 different cooling regimes for the same subject and coolant with 3 different results. Each one is absorbing a different amount of heat at a different rate.

All that to say this...

The chemistry of the coolant is extremely critical but by itself cant affect the cooling "process" much so in the end heat removal has to be looked at several ways
 
We've touched on coolant.. we are talking about oil and both of those carrying heat etc as well.

What about airflow over the engine?
 
We've touched on coolant.. we are talking about oil and both of those carrying heat etc as well.

What about airflow over the engine?

Same rules apply to oil- coolant is coolant, heat transfer is heat transfer

Airflow is extremely important for heat removal (to atmosphere). Me personally I would design as much as possible with electro-mechanical assistance.
 
Somewhat legendary for that but to address your point with an actual answer




For general conversation, that's close but not exactly right.

Lets say "heat removal" rather than cooling because that cycle is a 3 part triangle where the heat capacity of the "coolant" ( regardless of what it is really) is 1 part but that 1 part is constricted by the other 2.

So for discussion sake, lets take the "oil" out and substitute chemical X and lets say "X" has a heat capacity of .99 ( out of 1)

Step 2 is "volume and velocity" times the surface area. ( how much of "X" in terms of volume touch the surface of the heat to be removed and how long it sits there)- there's a limit to this because heat capacity is hard stopped by change of state of chemical "X" ( has to stay between)

Step-3 is removing the heat from "X" so it can go back and absorb more and continue the cycle.

Imagine this scenario- you have 3 steel plates ( say 6x6x1") heated bright cherry induction so they are through heated evenly

All for 10 minutes and with only 5 gallons

You squirt water on one side (covering the side fully) and it drains in a bucket

You have a bucket and do the lift/immerse for 10 seconds cycle

You drop it in the bucket and let it sit

That's 3 different cooling regimes for the same subject and coolant with 3 different results. Each one is absorbing a different amount of heat at a different rate.

All that to say this...

The chemistry of the coolant is extremely critical but by itself cant affect the cooling "process" much so in the end heat removal has to be looked at several ways
Ok, but you left out that I said "generally".

I've been around here awhile (not that it matters except in this context) I remember Bitog legends and others who were engineers who showed data in the early 2000's that showed "generally" thinner viscosity oils transfer heat better. But I don't have the time or desire to go dig those up. They are 10-15 year old threads.

Like I said, there may be some examples where it doesn't work that way, but I doubt most of us are seeing that with common oils. Is the difference huge? No way. The difference between a thick 20 weight and thin 30 weight is so narrow that manufacturing tolerances may overlap them at times. But I'd bet that almost any 20 weight will transfer heat better than almost any 50 weight. I'd be quite surprised to see otherwise. I'd be even more surprised to see a 50 weight (or even a 40 weight) with less density than a typical 20 weight, too. I think you'd have to look high and low for that. Btw, just for good measure, I do realize that the thicker oils tolerate the high heat better than thinner ones. (Generally. ;))

Btw, in the racing world, they've liked the idea of thinner oils with major emphasis on oil coolers. They'd go thinner than they do, except for the fact alcohol fuels shear the oils down dramatically. I'll check in with some of them to see their thoughts on heat transfer when I get a chance. I'll let you know what they say.
 
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Same rules apply to oil- coolant is coolant, heat transfer is heat transfer

Airflow is extremely important for heat removal (to atmosphere). Me personally I would design as much as possible with electro-mechanical assistance.

I had the engine changed in my car (bought it with a bum bearing. Or something. New to me engine was the cheapest route) and I seriously considered leaving the (huge, covers the whole engine bay) engine cover off.

The guy that did the work told me it is important for directing airflow around the engine and engine bay.

Would you agree with that? Or would just having as little impedance to ambient air (both ram air and less hot air cooling more hot things) be a better way to have it done, such as cars with no engine cover to speak of?
 
I've been around here awhile (not that it matters except in this context) I remember Bitog legends and others who were engineers who showed data in the early 2000's that showed "generally" thinner viscosity oils transfer heat better.

Sure and that's where semantics can cause a description to go off the rails- "thin" is a measurement of dimension, not density.

Density plays a part in the heat capacity of a given fluid

The thickness ( as in volume and area covering an item) affects transfer percentage and volume

They aren't the same and when they get lumped together is where things get misunderstood.
 
Sure and that's where semantics can cause a description to go off the rails- "thin" is a measurement of dimension, not density.

Density plays a part in the heat capacity of a given fluid

The thickness ( as in volume and area covering an item) affects transfer percentage and volume

They aren't the same and when they get lumped together is where things get misunderstood.
And I agree, but it is splitting hairs. So I'm going to continue to use thicker and thinner in this context because most oils' density will support it. But again, I do respect where you are coming from.
 
I had the engine changed in my car (bought it with a bum bearing. Or something. New to me engine was the cheapest route) and I seriously considered leaving the (huge, covers the whole engine bay) engine cover off.

The guy that did the work told me it is important for directing airflow around the engine and engine bay.

Would you agree with that? Or would just having as little impedance to ambient air (both ram air and less hot air cooling more hot things) be a better way to have it done, such as cars with no engine cover to speak of?

100%

That air needs to carry heat away and continuously replenish and it can be from straight heat rising or by flow ( or both)

Having an open air engine is fine ( and probably the best all around solution) but velocity and changes of air removing heat is more important in terms of actual heat removal.
 
I generally shut things down in the NSX when oil hits 275F. I've contacted Red Line and Mobil tech support folks and both agreed that was a relatively conservative limit. I have heard some Corvettes run hotter than that and that GM considers it just fine. Anyhow, 225F or so isn't even close to being a problem. I don't change my OCI because of heat. Maybe I'm doing it wrong.
 
Back to this:

In my Jeep, coolant temp heats up much more quickly than the oil. MUCH more quickly. It also cools much more quickly.

Of course the coolant heats up much more quickly than the oil ... that's pretty much true on any vehicle. The heating source for the coolant is mainly from the combustion in the cylinders, whereas for the oil heat of combustion is the minor heating source. So you are comparing apples and oranges with this analogy.

There are other variables at play but if not true, a liquid cooled engine would just cool the oil rather than bother with water. Water is thinner. It is also why a 50/50 water antifreeze mix cools better than higher percentage of antifreeze. For cooling, thinner is better.

You do realize that water has a higher density than motor oil (1 g/cm^3 vs ~0.86 g/cm^3 for motor oil), even compared to oil at room temperature. This is why oil floats on water. 50/50 mix of anti-freeze cools better because it's 50% water vs 100% antifreeze. Water has a relatively high specific heat capacity compared to other liquids, and that's why it's used so much for cooling applications. Water has about twice the heat capacity as motor oil for the same volume. Water is also less viscous than oil, even though it's density is higher.

The density of different viscosity motor oils is so close that if you did an experiment in an oil cooler and held everything constant except the oil viscosity, you wouldn't see much if any of a difference in the cooler performance (ie, hair splitting). From my research, it looks like the oil formulation has a bigger impact on it's thermal properties (thermal conductivity and specific heat) than the actual viscosity. If you have data that shows otherwise, please post it up.


And if you search for the word "viscosity" in this next reference you will see that they say that more viscous fluids increase a heat exchanger's performance.


Also, if you research heat exhangers, which is what an oil cooler is, you would have to determine what the specific heat value of the liquid is to determine the heat exhanger's heat removal performance. Specific heat of a liquid is not always a function of viscosity (ie, water).

Go to the section entitled "Heat Transfer Rate, Q" to see the heat transfer equation.

The heat capacity (Cp) of the oil would have to be determined, and as shown the Cp is not always a function of viscosity as shown by water properties and the link to the military paper. Same thing goes with oil ... even within the same viscosity, it's been shown that the heat capacity varies based on the oil formulation. So making blanket statements that "thinner motor oils cool better" has no validity unless you can show experimental data that is actually the case. From what I'm seeing, it's way more complicated that just that.

 
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So let's see this big revelation you have. Show me the study. I'd love to see it.

So you are tagging me for a belief, but you've presented simply an alternate belief with nothing more than a web discussion as support.

Your turn ... show me the study or any technical information that supports your claim that "thinner oils cool better". If the info is out there I'd actually like to see it. All you have is some comment based on what you "heard" 10~15 years ago. Lots of people make claims and never back it up with technical data/info. That's how misconceptions live on forever.
 
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As others said, 240-250F is acceptable for occasional romps but not desirable for regular cruising. Above 260F is concerning. If the oil spends any significant time above that, I would reduce the service interval by a thousand or 2. M1 0w40 is pretty stout.
 
Your turn ... show me the study or any technical information that supports your claim that "thinner oils cool better". If the info is out there I'd actually like to see it. All you have is some comment based on what you "heard" 10~15 years ago. Lots of people make claims and never back it up with technical data/info. That's how misconceptions live on forever.

Ok, I'll tell you what I just heard, directly, from the owner of 4Piston Racing, which makes Honda midget racing engines and drag racing engines that dominate their market and class. He has run many, many tests with varying oil weights to optimize performance in their engines. He's seen this consistently with racing oils, with thousands of hours on their dynos. Has never seen a thicker oil with data showing better heat transfer than thinner oils. Here is the direct quote: "Viscosity affects cooling, yes. Lower visc, faster heat transfer."

Btw, you can call him up and ask him yourself. Easy to look them up and easy to access him. And you can try, if you want, to tell him his data is wrong. That might give him a good laugh.

So everything on Bitog 10 to 15 years ago is wrong. Including people like AE Haas. Right.

It'll be neat to see a thicker oil that transfers heat better than a thin one. It will amazingly handle higher temps but shed them quicker. Best of both worlds. Can't wait to see it. Please share it with us ignorant folk. You are talking theoretical stuff with lab liquids handled by Dr. Bucent Honeydew and his assistant, Beeker. But we're talking commercially widely available motor oil. Let's see a motor oil I can go buy right now that does what you say.

Interesting that you think oil doesn't get anywhere near the combustion chamber. It gets as close to it as coolant does. And, unlike coolant, it is right at the source of friction. Right on the parts that produce it. Plenty close to the combustion chamber. But even if it were as you say, why does it cool off so much quicker than the oil? So, yeah, maybe it is apples to oranges. But the oil is the orange, and it lives in as hot a climate as any apple. Maybe hotter. The coolant is much thinner because it needs to be to do its job...pick up heat and get rid of it. It does that better than oil because it is thinner, meaning, lower viscosity, or as you'd like to say, less dense. Either way, thinner.
 
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Ok, I'll tell you what I just heard, directly, from the owner of 4Piston Racing, which makes Honda midget racing engines and drag racing engines that dominate their market and class. He has run many, many tests with varying oil weights to optimize performance in their engines. He's seen this consistently with racing oils, with thousands of hours on their dynos. Has never seen a thicker oil with data showing better heat transfer than thinner oils. Here is the direct quote: "Viscosity affects cooling, yes. Lower visc, faster heat transfer."

Btw, you can call him up and ask him yourself. Easy to look them up and easy to access him. And you can try, if you want, to tell him his data is wrong. That might give him a good laugh.

So everything on Bitog 10 to 15 years ago is wrong. Including people like AE Haas. Right.

You're "data point" is basically hearsay - regardless who it came from. Did your buddy actually put instrumentation on the inlet and outlet tubes of an oil cooler to see how different oil viscosity effected the in and out temperatures. And did he measure various oil temperature locations inside the engine? And if so, it would have to be done in an extremely controlled manner so only the viscosity difference effect would be seen. That's highly unlikely in an non-laboratory setting.

Keep in mind that thicker oils also create more shearing heat while used in an ICE, so that's another factor in the not so simple oil heating and cooling and resulting temperatures phenomena. But if you were to only look at the performance of an oil cooler as a function of oil viscosity then that would show how viscosity may have some effect. Another thing to realize is that if thinner oil has less specific heat capacity then it's temperature will drop lower with the same amount of heat removed compared to an oil with a higher specific heat capacity. As shown in my links, it looks like oil formulation itself has a large effect too, as the same viscosity rated oils can have very a different specific heat capacity. This isn't as simple as claiming that "thinner oils cool better".

If you or anyone else can not link up some good reference info showing testing results, then it holds as much weight as someone saying "The Earth is flat, because someone I know said so, and I think I "saw it" myself". Like I said, there are many factors involved, and if you actually read the links I posted you would see that.

It'll be neat to see a thicker oil that transfers heat better than a thin one. It will amazingly handle higher temps but shed them quicker. Best of both worlds. Can't wait to see it. Please share it with us ignorant folk. You are talking theoretical stuff with lab liquids handled by Dr. Bucent Honeydew and his assistant, Beeker. But we're talking commercially widely available motor oil. Let's see a motor oil I can go buy right now that does what you say.

Read the links, and go do some of your own searching and research information on the subject. Apparently you don't believe any research paper and only believe people who probably saw something in the wrong way, and misunderstood what they were actually seeing.

Interesting that you think oil doesn't get anywhere near the combustion chamber. It gets as close to it as coolant does. And, unlike coolant, it is right at the source of friction. Right on the parts that produce it. Plenty close to the combustion chamber. But even if it were as you say, why does it cool off so much quicker than the oil? So, yeah, maybe it is apples to oranges. But the oil is the orange, and it lives in as hot a climate as any apple. Maybe hotter.

Oil does not "get as close to the combustion chamber as coolant". Apparently you've never seen a head cut in half to show the water jackets surrounding a combustion chamber, or the cooling jackets surrounding the cylinders. The closest oil gets to the combustion chamber is under the piston crown when it's at TDC, and on of the water jackets that are located on top of the combustion chambers. Oil also picks up some heat from the ring pack, and from the cylinder walls when the piston is near TDC and exposing that area.

There have been many discussions in the past about where the heat inputs come from for both coolant and oil. Most of the heat input to the oil is from oil shearing and friction between moving parts. Some is from absorbed heat from hot parts heated up by combustion, but it's way less than you would think. Shannow provided a lot of information related to that subject matter.

The coolant is much thinner because it needs to be to do its job...pick up heat and get rid of it. It does that better than oil because it is thinner, meaning, lower viscosity, or as you'd like to say, less dense. Either way, thinner.

No, the coolant "picks up heat quicker" because of what was already discussed about it's density and specific heat capacity ... not because it's "thinner". I guess you missed the part where water is MORE dense than oil, not less dense like you said in the bold part of you post. Motor oil (regardless of viscosity) floats on water for a reason.

Anyway, it's apparent that you've got this misconception firmly planted, but I think it's really a misnomer until someone can actually prove that it's true.
 
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Forgot to add, that a less viscous oil (with all other things being equal) will run a bit cooler because it doesn't create as much heat from shearing. So it's possible for oil temperatures to run a bit cooler because of that factor. But that's not the same thing as saying "thinner oils cool better" (ie, like in the example of an oil cooler). The more correct statement would be something like "thinner oils don't generate as much heat, and therefore can run cooler under the same operating conditions".
 
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Forgot to add, that a less viscous oil (with all other things being equal) will run a bit cooler because it doesn't create as much heat from shearing. So it's possible for oil temperatures to run a bit cooler because of that factor. But that's not the same thing as saying "thinner oils cool better" (ie, like in the example of an oil cooler). The more correct statement would be something like "thinner oils don't generate as much heat, and therefore can run cooler under the same operating conditions".
You are both right.
Oil is cooled, dissipates heat, goes back heat transfer happens, and oil dissipates heat again. Regardless why oil is running coller, it is cooler. If oil temperature is 220f, it is having better cooling effect than oil that runs at 230f. Of course oil coolers are there to help dissipate heat faster and keep temperature in check so engine does not overheat in extreme conditions like track.
Thinner oils dissipates heat faster. Of course, if it was that simple we would all run 0W3 oils, but it is not that simple as here that saying also applies: thin as possible, thick as necessary, hence large sumps, different base stocks, oil coolers and other witchcraft.
 
I suppose it depends on the car, and how and where you drive it. Like more open roads, or say I-696.

I would think more during the warmer months I’d stick with the 5w tp keep it a bit cooler...I also feel the engine could use the extra “thickness” for a little fun driving...

For the colder months sounds like a good choice.

Another question....how stock is the car? :cool:
 
Anyway, it's apparent that you've got this misconception firmly planted, but I think it's really a misnomer until someone can actually prove that it's true.

To avoid possible confusion before I comment fully, what specific "it" are you referring to?
 
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