Synthetic and heat transfer

[Stelth]

Some years ago, I read an article in some sort of RV publication about synthetic oils. The article said that synthetic oils are better heat transfer fluids than conventional oils. It also said that since the pistons are basically oil-cooled, a synthetic would be better under severe conditions, such as a loaded-down motorhome climbing a hill.

Any truth to this?

 

[JHZR2]

Id comb through some spec sheets for base oils from the manufacturers and see if the heat capacity is much different.

A highr flashpoint wouldnt necessarily imply being a better heat transfer fluid, but it would resist coking and breaking down, as would the syn structure which is much more resistant to oxidation.

 

[Boatowner]

I know synthetics are generally considered to be slicker than conventional oil, which means engines should run a little cooler. Also, a synthetic is going to stand up to the high heat of hard running better. Whether any of that means synthetics transfer heat better I have no idea. However, in order to transfer heat the oil had to send it somewhere else, so I kind of doubt it.

 

[Astro14]

If the specific heat were the primary criterion for lubricants, we'd all be running water in our engines...

I find it hard to believe there is any appreciable difference in specific heat among fluids made up of groups of hydrocarbons that are basically the same construction (between conventional and synthetic)

 

[skyship]

Sort of, but keeping the engine clean inside is more important as sludge reduces oil flow and major brand full synthetics clean better than some Iffy lube or supermarket special. This is more important in race engine terms than for a motorhome diesel.

 

[aquariuscsm]

I`d be willing to bet that was back when synths were pao/ester based before the grp III`s came along.

 

[Boomer]

Another way to check is to look at the density of the fluids. Higher density fluids may be less effective at transferring heat as they absorb more calories to get toa given temperature.

 

[HerrStig]

Originally Posted By: Boomer
Another way to check is to look at the density of the fluids. Higher density fluids may be less effective at transferring heat as they absorb more calories to get toa given temperature.
Why, then, did the Navy try a LIQUID SODIUM cooled reactor in the first Seawolf? It didn't work out, BTW so they retrofitted a water cooled unit.

 

[dparm]

Originally Posted By: Boatowner
I know synthetics are generally considered to be slicker than conventional oil, which means engines should run a little cooler. Also, a synthetic is going to stand up to the high heat of hard running better. Whether any of that means synthetics transfer heat better I have no idea. However, in order to transfer heat the oil had to send it somewhere else, so I kind of doubt it.



Slicker? What do you mean?

 

[DBMaster]

I can only speak about Mobil 1 and Amsoil. Amsoil claims that engines run 20-50 degrees cooler with their oils. A friend of mine damaged the fan shroud on his 88 Thunderbird (3.8L V6) which caused it to start running hot. Using Mobil 1 kept the temperature in the normal range. The Amsoil rep I knew called it the effect of laminar flow v. turbulent flow.

 

[JHZR2]

Originally Posted By: aquariuscsm
I`d be willing to bet that was back when synths were pao/ester based before the grp III`s came along.


So cite a difference in heat capacity before making claims that are just out there. I know plenty of folks have a hatred for grp III, but spreading fallacies does not do anything for your case.

 

[JHZR2]

Originally Posted By: DBMaster
I can only speak about Mobil 1 and Amsoil. Amsoil claims that engines run 20-50 degrees cooler with their oils. A friend of mine damaged the fan shroud on his 88 Thunderbird (3.8L V6) which caused it to start running hot. Using Mobil 1 kept the temperature in the normal range. The Amsoil rep I knew called it the effect of laminar flow v. turbulent flow.



Totally uninformed amsoil rep. Do you even know what laminar and turbulent flow is?

You can start by reading up on reynolds number. Given that the viscosity of a syn vs a conventional oil with the same grade and HTHS will be the same, what else is changing in that equation to magically increase the reynolds number?

 

[JHZR2]

Originally Posted By: Boomer
Another way to check is to look at the density of the fluids. Higher density fluids may be less effective at transferring heat as they absorb more calories to get toa given temperature.


If you can find density, then you can find heat capacity, which tells you specifically how much energy it takes to raise one gram on kelvin.

 

[Kiwi_ME]

My marketing B*S detector is buzzing on this one.
Nor is thermal resistance the same as thermal capacity. The two seem to be confused in this post.

 

[JHZR2]

Originally Posted By: Kiwi_ME
My marketing B*S detector is buzzing on this one.
Nor is thermal resistance the same as thermal capacity. The two seem to be confused in this post.


I highly doubt that any value of any sort between a bunch of different motor oils have any appreciable difference.

Of course, put solids in and we may have another story:

http://www.greencarcongress.com/2012/02/rice-20120202.html

But that's not how motor oils are formulated. The difference in thermal conductivity between say, motor oil, engine oil and a low weight machine oil is at the second decimal place.

 

[Hyde244]

Synthetic is first recommended for severe service, such as towing.

Since synthetic is more refined, the oil molecules are of a more consistent size, meaning less friction, and less generated heat.

Since the average synthetic oil molecules are also of a smaller size than the average conventional molecule, the molecules are able to get into more areas of the engine, which I would imagine is the reason for better cooling claims.

If you are doing hard towing or operation, it is definitely worth considering using synthetic - that is exactly what this genre of oil was designed to do.

Here's a good Car and Driver video clip discussing the differences:

 

[JHZR2]

Originally Posted By: Hyde244
Synthetic is first recommended for severe service, such as towing.


Agreed. But for reasons way beyond some hokey cooling or flow claim.

Quote:


Since synthetic is more refined, the oil molecules are of a more consistent size, meaning less friction, and less generated heat.



Have GC or GC/MS results to validate that claim? There is still going to be a major distirbution of products from a synthesis reaction. The catalysis is NOT that selective.

Quote:


Since the average synthetic oil molecules are also of a smaller size than the average conventional molecule, the molecules are able to get into more areas of the engine, which I would imagine is the reason for better cooling claims.


Again, data? Its easy to get a molecular weight distribution of a finished product to prove this or disprove this. Given that additives such as Z-max have been effectively disproven on here, when this mechanism was stated as the way they work, what gives syn oils a free pass?

Quote:


If you are doing hard towing or operation, it is definitely worth considering using synthetic - that is exactly what this genre of oil was designed to do.



Yes, due to a resistance to oxidation, and a better viscosity index and HTHS value and higher film strength. Its also valid for flow at very cold starts. But none of those directly reflect the claims youve made.

 

[dave1251]

Originally Posted By: Hyde244
Synthetic is first recommended for severe service, such as towing.

Since synthetic is more refined, the oil molecules are of a more consistent size, meaning less friction, and less generated heat.

Since the average synthetic oil molecules are also of a smaller size than the average conventional molecule, the molecules are able to get into more areas of the engine, which I would imagine is the reason for better cooling claims.

If you are doing hard towing or operation, it is definitely worth considering using synthetic - that is exactly what this genre of oil was designed to do.

Here's a good Car and Driver video clip discussing the differences:



I do not use car and driver as a reference for what lubricant I should use, in actual use most IC engines today do not push the boundaries to make a difference between a conventional and a synthetic PCMO because the quality of ISLAC/API certified lubricants is very close we are comparing a ham dust of a difference. Now lets take the way back machine to 1996 then this is a different discussion.

 

[aquariuscsm]

Originally Posted By: JHZR2
Originally Posted By: aquariuscsm
I`d be willing to bet that was back when synths were pao/ester based before the grp III`s came along.


So cite a difference in heat capacity before making claims that are just out there. I know plenty of folks have a hatred for grp III, but spreading fallacies does not do anything for your case.


I`m not citing or making any claims,I made a basic assumption. How would conventional oil be different from conventional oil? I never made a claim of temp differences,I was making an assumption on the op`s claim. A case? Huh???????

 

[dave1251]

Originally Posted By: aquariuscsm
Originally Posted By: JHZR2
Originally Posted By: aquariuscsm
I`d be willing to bet that was back when synths were pao/ester based before the grp III`s came along.


So cite a difference in heat capacity before making claims that are just out there. I know plenty of folks have a hatred for grp III, but spreading fallacies does not do anything for your case.


I`m not citing or making any claims,I made a basic assumption. How would conventional oil be different from conventional oil? I never made a claim of temp differences,I was making an assumption on the op`s claim. A case? Huh???????



You are aware PAO is "conventional" oil also right?