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I would guess it has someting to do with the amount of friction modifier added. Since friction modification can occur thorough use of moly or an ester base oil (and probably a plethora of other factors), it is not going to be easy to quantify IMO.
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Ask Merkava 4. He likes to use that word.
I almost brought it up this morning in that thread that he used the term but I figured it not worth it.
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We can certainly come up with what it might mean (like coefficient of friction) but I think the point is made-up words for physical properties should not be used in technical discussions.
Given that there are many states of lubrication, which are discussed here: http://www.bobistheoilguy.com/states of lubrication.html, and that the amount of total friction (fluid + possible metal to metal) will vary depending on the state, this concept cannot be simplified in a way that does not reference what state(s) are being discussed.
I think it is well established in engineering books that the lowest total friction occurs approximately when the film thickness is just thick enough to prevent metal to metal contact. That's just for ONE lubricated assembly (bearing, etc). An engine has so many different parts (and operating conditions) with different ideals as far as viscosity and additives are concerned that the oil for least total power loss due to friction is a compromise for all the different parts. It is most likely that in an engine you could keep trying thinner and thinner oils to the point that total friction would keep decreasing while excess wear on SOME parts keeps increasing. That's the compromise some race engine engineers have to make.
Ok, with all that said. I think a good, technically legit phrase that can replace "slipperiness" is total friction, which is the sum of fluid friction and metal to metal friction. All who agree, say yay?
If we all get savvy with the different states of lubrication and how often the different parts of engines spend time in each of those states, we will be on our way to being uber engine lubrication geeks.
I don't think a higher HTHS really has any correlation to "slipperiness." Thinner (to a point before metal to metal contact), more friction modifiers (to a point before overloading the oil with FM), higher group base oil--I think all these contribute to "slipperiness." There may be a trade off at the thinner end where you can gain some "slipperiness" by going a bit thinner than should be and compensate with a higher HTHS, but it probably is not a noticible difference and may counteract cancelling out any gain. Who knows? Why worry? The difference is infinitesimal!Quote:
I thought slippery was basically a low(er) cSt @ 100 but a higher HT/HS. Wouldn't that naturally logically define a slippery oil because on the one hand you are thinner(less friction then a thicker oil) but you still protect because of the high(er) HT/HS?
or can you have a high cSt @ 100 *and* a high HT/HS??
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I thought slippery was basically a low(er) cSt @ 100 but a higher HT/HS. Wouldn't that naturally logically define a slippery oil because on the one hand you are thinner(less friction then a thicker oil) but you still protect because of the high(er) HT/HS?
or can you have a high cSt @ 100 *and* a high HT/HS??
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Yes, you read the title correctly.
Can someone explain what is the property of "slipperiness" as related to a PCMO oil and please direct me to the product data sheet number or ASTM test that measures this property/quality?
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Yes, you read the title correctly.
Can someone explain what is the property of "slipperiness" as related to a PCMO oil and please direct me to the product data sheet number or ASTM test that measures this property/quality?
Would you like the results of that test to show the most slipperyness at cold start-up (or) normal engine operating temperature?
My definition of cold-start slipperyness is something I have been doing for the past 30 years changing my own oil. Prior to pouring the new oil, I rub some (0W/5W/10W-30) on the tips of my forefinger and thumb. It's my own friction test - rubbing back & forth for around 10-15 seconds.
Which "COMMON-EVERYDAY FOUND" oils feel the slippery(est) between my fingers?
1) a)Pennzoil Platinum - b)Castrol GC 0W/30
2) a)Castrol Synthetic Blend - b)Motorcaft Syn-Blend
3) a)Pennzoil yellow bottle - b)Valvoline All-Climate
I never thought about doing it right after the oil change. Perhaps because the oil is just too darn hot.