Synthetic Oil- not more "slippery"...yet lower CF?

[lomez]

This one has always made me scratch my head. Maybe it's a dumb question, but.....I have always read that "synthetic oil is not more slippery" (usually in response to "bubba" the mechanic's claim that you should use synthetic oil during "break-in"). Then, in serious lubrication journals and papers, I will read "__________ will benefit from synthetic oil due in part to its lower coefficient of friction......"

So, Group III/IV/V base is not more slippery, but has an inherent lower CF? Someone help me understand the very layman's "slippery" compared to the more technical "coefficient of friction".


Thanks!

 

[Rand]

there are different kinds of friction and additives.

and generally speaking there are all kinds of people out there who try to explain it and fail badly.

I'm not even going to try.

There are a few on here I would definitely listen to..

and quite a few more I wouldnt.

 

[lomez]

Edit- In the "bubba" example above, I meant to say that Bubba the mechanic tells people they shouldn't use synth during break-in (accidentally typed should)
...just in case it confused

 

[NHGUY]

Strange,cant use syn during break in but GM Dexos spec and Chrysler spec is mostly syn or syn blend now...from the factory...new.

 

[MolaKule]

People making those kinds of statements are simply misinformed.

Quote:
Definition of SLIPPERY
1a : causing or tending to cause something to slide or fall b : tending to slip from the grasp
2a : not firmly fixed : unstable b : not precise or fixed in meaning : ambiguous, elusive
3: not to be trusted : tricky
— slip·per·i·ness noun


Slippery is one of those ambiguous weasel words often used to confuse the issue.


The coefficient of friction is the proper term for describing one of the characteristics of a lubricant/surface interface. Synthetic base oils have a lower coefficient of friction than do mineral oils.


To further de-confuse the issue in regard to run-in oils, what you want in a run-in oil are anti-wear additives such as ZDDP and boron or polymer esters, but what you do not want are friction reduction additives like Moly, Antimony, Titanium, Tungsten, or GMO.

My take is with the proper run-in addtives (anti-wear additives minus the friction modifiers) it matters not what the base oil might be.

 

[Rand]

There are also 2 kinds of break in..

factory engine..


and rebuilt/aftermarket engines.

 

[bepperb]

Originally Posted By: MolaKule


Slippery is one of those ambiguous weasel words often used to confuse the issue.




Hey, I only use those ambiguous words to make it sound like I know more than I really do, and so that I can argue I wasn't wrong but was just mis-interpreted when I really was wrong. What's so weasely about that?

 

[MolaKule]

Originally Posted By: bepperb
Originally Posted By: MolaKule


Slippery is one of those ambiguous weasel words often used to confuse the issue.




Hey, I only use those ambiguous words to make it sound like I know more than I really do, and so that I can argue I wasn't wrong but was just mis-interpreted when I really was wrong. What's so weasely about that?

 

[lomez]

Thanks molakule et al. That makes sense.

As for "break in"....correct, there are rebuilt engines done mostly at a machine shop, and there are new engines from a $billion engine factory. Nowadays, new vehicles don't need "breaking in". If anything at all, just dump the factory fill and re-fill after 500 miles and then forget it. My 327 that I had rebuilt .060 over with a monster cam....yea, that probably needs a break-in period for the rings to seat.


Molakule, if you're still looking at this one...can you give me a little more education on the difference between friction reducers and the anti-wear additives? Can I take it that a wear reducer is one that will cushion a contact point (such as valve seats and meshed gears)...and provide barrier protection, but not be particularly good at reducing the CF? While the friction reducer does the exact opposite? I always considered moly to be a wear reducer...no? or does it (MSO2) do both?

Thanks in advance!

 

[Garak]

Originally Posted By: MolaKule
The coefficient of friction is the proper term for describing one of the characteristics of a lubricant/surface interface. Synthetic base oils have a lower coefficient of friction than do mineral oils.

How much do additives affect the µ of an oil versus the base stock itself, Molakule?

 

[440Magnum]

Originally Posted By: lomez
Thanks molakule et al. That makes sense.
Nowadays, new vehicles don't need "breaking in". If anything at all, just dump the factory fill and re-fill after 500 miles and then forget it. My 327 that I had rebuilt .060 over with a monster cam....yea, that probably needs a break-in period for the rings to seat.


!



Now you're going to have all the Honda guys yelling at you that if you don't leave the factory fill break-in soup loaded for a FULL oil change interval, you'll be missing out on all that special factory goodness ;-)

IMO, all engines still need a bit of break-in. The factories may be more precise now, but that doesn't mean that the parts are manufactured pre-bedded together- the bores are still cut with a rotary boring tool and finished in a cross-hatch, and that manufacturing pattern has to be worn-in to the piston and rings' installed reciprocating motion. It may happen much more quickly on a modern roller-cammed engine that doesn't have to seat the tappets to the cam lobes, but there's still some break-in. I know at lest one new car manual that still addresses driving habits during break-in, the SRT-8 manual goes so far as to imply you should keep it below highway speed for the first 50 miles, and still has language about avoiding WOT/high RPM and cruising too long at a constant speed for the first 1000 miles.

 

[MolaKule]

Quote:
The critical difference between AW/EP additive films and FM films is in their mechanical properties. AW/EP films are semiplastic deposits which are hard to shear off. Thus, under shearing conditions, their coefficient of friction is moderately to high. The exceptions are the organometallic compounds listed above. Friction modification films consist of orderly, close-packed arrays of multimolecular "whiskers," loosely adhering to each other. The outer layers are sheared-off easily, allowing for low coefficient of friction. The phenomena can be described as a deck of plastic coated playing cards lying on the table and sliding off the top card easily.



Another example of how friction reducers work is thinking of a mower shearing off the top of grass. When you go back over an area that had the grsss sheared off, it is easier to push the mower.

 

[MolaKule]

Quote:
I know at lest one new car manual that still addresses driving habits during break-in, the SRT-8 manual goes so far as to imply you should keep it below highway speed for the first 50 miles, and still has language about avoiding WOT/high RPM and cruising too long at a constant speed for the first 1000 miles.


But isn't that procedure more directed at keeping the temperatures down during inital run-in than anything else?

 

[MolaKule]

Friction Modifiers and AW additives:

https://bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=729029#Post729029

 

[MolaKule]

Quote:
How much do additives affect the µ of an oil versus the base stock itself, Molakule?



Let's say a nonlubricated surface, such as a rectangular plate of polished steel-on-steel, tested as having a COF of 0.60.

A non-additized mineral base oil may reduce COF to 0.20.

A Friction reduction compound added to mineral base oil might reduce it to 0.07.

 

[Garak]

Thank you, Mola! That's the kind of data that will keep us honest.

 

[440Magnum]

Originally Posted By: MolaKule
Quote:
I know at lest one new car manual that still addresses driving habits during break-in, the SRT-8 manual goes so far as to imply you should keep it below highway speed for the first 50 miles, and still has language about avoiding WOT/high RPM and cruising too long at a constant speed for the first 1000 miles.


But isn't that procedure more directed at keeping the temperatures down during inital run-in than anything else?


Possibly and in fact likely... butsome process must be going on in the engine that doesn't continue after that initial run in. And that still leads me to believe that that when you manufacture with one cutting orientation (no matter how precise the cutting process is), and then operate with a different orientation, there is going to be an initial break-in or wear-in process that needs some special control.

And yes, that's all speculation/extrapolation on my part- my point being simply that I don't believe that its true that "modern engines don't need a break-in." The break-in they need may be almost invisible to the operator, but it still happens and if you want the thing to last to its full potential, awareness is still beneficial or they wouldn't address it in the manual.

 

[440Magnum]

Originally Posted By: MolaKule
Quote:
How much do additives affect the µ of an oil versus the base stock itself, Molakule?



Let's say a nonlubricated surface, such as a rectangular plate of polished steel-on-steel, tested as having a COF of 0.60.

A non-additized mineral base oil may reduce COF to 0.20.

A Friction reduction compound added to mineral base oil might reduce it to 0.07.




So in that example, the mineral base oil causes a factor of 3 reduction in COF, and the friction modifier contributes almost another factor of 3. What would the split be with a synthetic base? Would the total reduction in COF be about the same, with the split being a bit different (more due to the base itself, less due to the additive?) Or is any difference trivial compared to other factors?

 

[MolaKule]

The answer to that question depends on whether you're referring to a PAO, PAO with synthesized esters, PAO with biosynthetics, biosynthetics with synthesized esters, etc.

 

[440Magnum]

Originally Posted By: MolaKule
The answer to that question depends on whether you're referring to a PAO, PAO with synthesized esters, PAO with biosynthetics, biosynthetics with synthesized esters, etc.



I guess there's no generalized answer, and that in itself is an answer. I was getting at the competing claims that "the only advantage to synthetics is longer life" vs. "synthetics also reduce wear". I personally think that synthetics a) are more consistently good than conventionals, and b) do offer some advantage in wear protection other than just longer OCI. But I also freely acknowledge that good maintenance practice with a quality lubricant is probably sufficient to render any difference between synth and conventional unnoticeable over the life of the car.

I'm just one of those guys who thinks the small price difference over the life of a car is such a small part of the total cost of ownership that it makes it worth buying synthetic... even if its just a peace-of-mind matter. I do not understand saving a few dollars per quart of oil when you're talking about a machine that may represent $30k, $50k, or well over $100k total cost of ownership by the time you throw in fuel, tires, batteries, shocks, registration, inspections, insurance, and the cost of the vehicle itself.