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.