Synthetics and polarity/surface tension

[FCD]

Some people in the classic car world, and i've read people say it on this board too, say that conventional oils are better for classic cars that are used infrequently, since they "stick" to the parts of the engine more than synthetics which have a lower surface tension it seems and drain away from the engine parts quicker so at startup when most of the oil is in the sump there will be more residual oil left on the engine parts.
Is there any truth to this? Is there any particular group of oil that sticks to engine parts better than others?

 

[Ohle_Manezzini]

Nope, specially after a week or so, you wouldn't have any oil on upper parts. Those special "smart" [esters] molecules give you, at most 24 to 48 hours more of film, not a week or two. At the end, gravity wins polarity. Unless you get tacktifiers, but they are an oxidation problem, IMO.

 

[AirgunSavant]

Dirty oil sticks best

 

[CT8]

Syn oil are blended to achieve the most desirable properties that a lubricant needs to do the job. This isn't the 1970s any more though the marketing still is.

 

[Virtus_Probi]

Molakule posted this way back in 2003, I hope he doesn't mind me quoting him.
"Firstly, higher surface tension does not equate to better oil clinging.

In the Global View, the macroscopic world, what makes oil cling is the tackifiers in the oil. What makes the oil spread is an additive called a surfactant, such as Schaeffer's penetro additive in 132 and their motor oils. The surfactant actually "reduces" the surface tension so the additives can move into the the small metal valleys.

One the microscopic scale, chemically polar components of the addtitives, such as sulfur and phosphorus, cause the addtive to bond to the metal. If the addtive is ZDDP or MoTDC, the polar attractive chemicals cause the zinc or moly to "bind" to the metal's surface.

Esters, which are more chemically polar than Group I,II or III mineral oils and PAO's, also imbed themselves into the metal in a similar fashion to ZDDP and MoTDC.

A well formulated synthetic that contains esters will have better metal adhesion protection than will a dino."

https://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=22151

 

[FCD]

MolaKule is very savvy on these things and what he says makes sense to me really, i'll take his word.

 

[Ohle_Manezzini]

Yes, but, as not mentioned, not for 300 + hours of inoperation, as commonly happens to classic cars. Esters buys time, but in no way means permanent lubrication forever.

 

[DrRoughneck]

Originally Posted By: Ohle_Manezzini
Nope, specially after a week or so, you wouldn't have any oil on upper parts. Those special "smart" [esters] molecules give you, at most 24 to 48 hours more of film, not a week or two. At the end, gravity wins polarity. Unless you get tacktifiers, but they are an oxidation problem, IMO.

What he said, with the right words like he said.

 

[MolaKule]

Originally Posted By: Ohle_Manezzini
Yes, but, as not mentioned, not for 300 + hours of inoperation, as commonly happens to classic cars. Esters buys time, but in no way means permanent lubrication forever.


So, what happens to the polar additives that were last deposited onto the metal before the engine stopped?

 

[53' Stude]

LOL! Thanks for the info and wisdom Molakule

 

[Ducked]

Anecdotally, and ..er..macroscopically, if you insist, when you take an engine apart that's been sitting in a scrap yard for a decade or so, its got oil on it.

I had a peer into the engine of an abandoned Stuart M3 tank (pretty macroscopic, I hope you'll agree) a while ago. Flathead Cadillac sidevalve, probably last run in the 50's. It had oil on it.

I dunno what sort of oil, but I'd guess it wasn't synthetic, or multigrade, and I'd guess if I'd had a microscope, it'd have had oil on it microscopically as well.

 

[oldhp]

Anybody ever take apart a engine that has been sitting for long time? 1966 327 engine, sitting a long time, oil droplets on camshaft lobes, lifters still had oil in them, piston rings still had oil in ring landings, cylinder walls still had oily film. You could have started this thing right up. I've never taken a engine apart that has been bone dry, let alone sitting for a couple of weeks or months.

 

[BrocLuno]

This is really easy to test. Get a full synthetic 10W-30 and your standard filter. Change the oil. Drive it around some and park it. Let it sit for 3 or 4 days. Open the hood. Start the motor. Do you hear clicking and clacking? How about low thumping (rods)... It'll go away in a few minutes, but ...

Now do the same thing with a quality dino 10W-30. Same grade, same test. What do you hear?

If no difference, your motor does not care - use what you want. Try that in my Bronco, and the syn will scare you half to death. Any decent dino - quiet as a mouse

Why - surface tension does not equate with "cling". It equates to capillary fill. Same two oils an a 0.1mm pipette. Which oil raises further in the capillary space?

That is what a plain bearing is when it's not turning. It's a capillary space. You would like it to be full when you hit the starter. With syns it is often not the case ...

Let your individual motor tell you what it wants... Listen. It'll tell you

 

[oil_film_movies]

Castrol Magnatec gets its "startup protection" from polar molecules. Might be similar to what's in "Hyper-Lube" or "Lubegard Bio/Tech", some form of esters. (Not necessarily same as polyol esters in Redline oil and others.) Slimes the metal surface after shutdown, ready for startup next time. http://www.vento.com.vn/docs/en/Surfactants/Lubricant additive/Lubricant Additive.pdf

 

[FCD]

I do have a friend who used Mobil 1 0W40 in an old Ford Kent crossflow engine ( fat tappet ohv I4 ) and he told me the engine was rather noisy on it, then i told him to use a Dino 15W40 HDEO and the engine was quiet again...

 

[BrocLuno]

Originally Posted By: oil_film_movies
Castrol Magnatec gets its "startup protection" from polar molecules. Might be similar to what's in "Hyper-Lube" or "Lubegard Bio/Tech", some form of esters. (Not necessarily same as polyol esters in Redline oil and others.) Slimes the metal surface after shutdown, ready for startup next time. http://www.vento.com.vn/docs/en/Surfactants/Lubricant additive/Lubricant Additive.pdf


All motor oils do this. Syn, Dino - they all leave a film. The question is how thick is that film ... Engines are never dry unless opened up to the atmosphere and left for months, or years ... They always have a coat of "slime" on all internals...

Think steam locomotives and make-&-break engines. Everything is out in the open and they run fine. Some oil here and there (for the locomotive it was the job of the oiler [person] to fill the cups at each water stop). Make-&-breaks will run all day with morning lube. Once lubed, they have residual film. As a matter of fact, it is actually hard to get the oil off/out of the metal. You have to "boil" it in a caustic wash solution like the machine shops do.

But cold film thickness is different than the mere presence of oil on the surface ...

 

[4WD]

Amen - they tend to not be SST and have not seen much rust in them.

 

[Ohle_Manezzini]

Originally Posted By: MolaKule
Originally Posted By: Ohle_Manezzini
Yes, but, as not mentioned, not for 300 + hours of inoperation, as commonly happens to classic cars. Esters buys time, but in no way means permanent lubrication forever.


So, what happens to the polar additives that were last deposited onto the metal before the engine stopped?


What deposited additives you mean? Tribofilms from chlorinated, AW (ZDDP), Moly, other EP, antirust...? Well, deposited additives, like zddp, forms the called glass layer, isn't like a permanent oil film, the oil detachs from the glass add as it is formed to the parts. So, the oil film run down when the engine is sitting, leaving the deposited add behind. The reacted additive layer isn't liquid as the base oil that carried it to the parts on the formation. As you know, for example, zddp reacts to the Fe on the parts to make the phosphate glass. Those films aren't part of the base oil, but a good detergent dispersant pack could strip them out...
The antirust add is needed because the oil will leave the parts after a longer period of sitting time, and the phosphate glass play that role pretty well when the parts are exposed to air/humidity...