Justify syn over dino because of better 'dynamic shearing'?

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Jan 7, 2003
Colorado Springs
Hi, it has been said that syn will shear less then dino oils under load(basic Redline positon and BOSISTHEOILGUY has stated it in a post also). This less shearing, for lack of a better term, I will call it 'dynamic shearing' is when the VIIs align themselves under load and recoil back under less load. Since most agree a syn, like Mobil1 10W-30, has less VII, its 'dynamic shear' should be less the a typical dino oil. So this seems to justify somewhat the use of sys with all things else being equal and load a consideration. Of course, this presumes that the shearing under discussion really affects wear and is not just some measurable artifact but of little real world interst other than marketing copy by syn oil producers. What do you guys think? Is this some point to consider? I don't usually hear this point in the syn vs dino wars. It if is something to consider, it seems to be an attribute that only a syn can offer since it has less VIIs. Thanks BTW, Redline web site says that a dino 10w-30 oil will shear back to a 10 under load and has a chart showing the shearing under increasing loads. Of course, Redline does well. I assume any other low VII syn like Mobil1 10W-30 would be similar. However, wide range syns like 0W-40 might be a different story. [ September 03, 2003, 03:30 AM: Message edited by: Fillherup ]
Originally posted by Fillherup: It if is something to consider, it seems to be an attribute that only a syn can offer since it has less VIIs.
I think you hit the nail on the head there. Less VIIs = less shear under load compared to a similar viscocity dino. However a wide spread vis like 5W-50 syn will probably shear down similar to a 10W-40 in the bearings I would believe. Also PAOs and especially ester basestock have higher natural anti-shearing properties. Btw, I still dont think the differences are that huge. M1 0W-40 has a HTHS of 3.6 where as Castrol GTX 15W-40 dino has ~4.0. Yes I know the M1 is 0W... A mineral 0w-40 (if there was such one) would have a very low HTHS. But I think I know which oil is gonna give me more protection [Smile]
When a person states that an oil has "sheared down" from one grade to the next lower, how does he qualify that statment? Ima' slow learner but ain't dynamik shear gots ta du with viskosity n sumpthin' ta do wit whethers a oryls frikshun modified er not?
Leo, Not sure how close HT/HS tracks with the dymanic/temp shearing. Since most 10W-30 oil, dino or sys, have similar HT/HS of around 3, the HT/HS must not be able to reflect it completely. But I would expect at least some relationship. BTW, I pulled down some HT/HS SAE reports about a year ago and the HT/HS does track to wear better than just oil viscosity at 100C. Also, they used the same base stock but added VII to modify the HT/HS during the test. So all this focus on viscosity is probably misplaced and the UOAs never measure HT/HS. I would have more interest in a UOA if I could get a HT/HS reading. One thing I have never been able to understand is the relatonship of HT/HS and viscosity. Generally the higher the viscosity the higher the HT/HS. But you can find SAE 30s oils that have equal or higher HT/HS than SAE 40s. The exceptions are a mystery to me. [ September 04, 2003, 12:47 AM: Message edited by: Fillherup ]
Userfriendly, Good question, I don't know how they measure it and wonder myself. Regardless, Redline seems to think they can. See link below and look at Figure 1. Figure 2 is for HT/HS. Also, they claim that dino can not do it and only claim for their syn. But I would expect a low/none VII oil like Mobil1 10W-30 to be similar. If one buys into this argument, than this is a pretty compelling reason for syn regarless of drain intervals, temps, etc. I would go syn just based on this chart. Just hope it true and not misleading. I am surprised that it not talked about more on the forum. It seems per Redline to be a syn( or at least their oil) unique feature/benefit over dino.
From Redline oils: The viscosity seen in a bearing or cam may be completely different than the labeled viscosity. Petroleum oils lose considerable viscosity at high RPMs and high temperatures. In contrast, Red Line synthetics are much more resistant to viscosity loss than even the best petroleums. A petroleum 20W50 begins as a 20W oil and the oil is thickened with a polymeric plastic substance which will thicken the oil at higher temperatures. Unfortunately, when the oil enters a high shear stress area such as a bearing, these large polymer molecules align themselves in order to create the path of least resistance. As shown in Figure 1, the apparent viscosity can be much less than the viscosity listed on the container - typical 20W50s will actually be similar to an SAE 30 or 40 in the bearing. The same behavior occurs with all multigrades, with a petroleum 5W30 shearing down to a 10W or 20W and a synthetic 5W50 shearing similarly to a petroleum 20W50. No wonder 5W30s are not recommended for sustained high-speed driving.
Redline technical data with shear charts Fig 1 [ September 04, 2003, 12:38 AM: Message edited by: Fillherup ]
Ben Dover and Fillherup; Look at the first two sentences. In part: Petroleum oils lose viscosity at high rpm.... What affect does rpm have on viscosity? The viscosity seen in a bearing or cam... He talks about the bearing (area) as being a high shear area. Is he referring to dynamic shear, which I think is kinda' related to flow and viscosity? The oil ON a camshaft, not in a cam...... I would guess that is a different kind of shear, the load carrying capacity of a lubricant that is reduced with viscosity loss as the oil is heated. I dunno' this stuff is over my head. The entire document looks like a scare tactic. If that sort of scientific gobbledegook sells oil, well so be it. The sales pitch doesn't influence me one way or the other. [ September 04, 2003, 12:59 AM: Message edited by: userfriendly ]
But Userfriendly, this is our beloved Redline oil. They would not lie or just market to us -right? [Big Grin] Actually, I kind of buy into the argument. I have heard it mentioned beyond just RL. RL is just vocal and has charts to back up their claims. BTW, I do use RL in MT 90 and D4, but not their motor oils due to cost and availability.
Is the Exxon/mobil merge and purchase of BP Air going to tighten the ester base stock market? Red Lne could have said; By reacting polyhydric alcohols with fatty acids produces the ester base stock. Then made a reference to the airline industry and ETOs. Instead of referring dynamic shear in areas of high mechanical load, such as the cam and lifter contact patch and gear loading, Red Line could have referred to the special additives blended into their lubricants which gives Red Line its load carring advantage over engine and gear oils blended from conventional and other synthetic base stocks. Now that type of advertising would likely help Redline sell oil instead of playing down to their potential customers.
Redline's statements about the long chain molecules aligning and reducing the viscosity make a lot of sense. After all, viscosity improvers only make the oil act as a higher viscosity. The oil is still just a 10, 5 or 0 weight at heart. Under extreme load, whats not to make thes long chain polymers lay down flat, reducing the instantaneous film thickness. Nothing. A true 40 or 50 weight oil has molecules that aren't long chains, but rather large octagons or rectangles that would physically have to break down to reduce their viscosity and reduce the film thickness. I don't think this is a Syn vs. Dino issue, I think its more about the viscosity spread and amount of viscosity improvers. [Big Grin] Just my 2 cents.
Originally posted by crashz: I don't think this is a Syn vs. Dino issue, I think its more about the viscosity spread and amount of viscosity improvers.
If it's a vis spread issue, that makes it a syn vs. dino issue because dino needs more VIs to make the same spread.
How does that translate to gear and transmission fluids when not one or the other base stock types have VI improvers? It is interesting that helicopter gear reduction transmissions can get away with a 5 cSt (ETO) ester based lubricant. Here is my question: Can gear lubes blended fron ester base stocks get away with using a lighter viscosity than mineral based lubes? If both types of lubricants were operated over a long period of time at a constant service temperature, would one have an advantage over the other in wear numbers? Do the esters require more or less additives to achieve say a GL-5 protection level than mineral based lubes? Are the esters in the automotive type applications equivalent to generation III aircraft turbo lubricants, just a higher cSt? Do these surface transportation ester lubricants have a higher natural mechanical load carrying capacity than mineral, PAO, or group III based lubricants, and therefore offer a longer service life, instead of being dependent on high levels of additives?
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