Oil molecules are subject to both shearing (This is in addition to the VII polymers shearing back.) and oxidation. These molecular changes definitely constitute a "wearing out" of the lube base stocks. The idiot who started the urban myth that "motor oil does not wear out" in order to sell his toilet paper oil filters should be boiled in unfiltered worn-out motor oil...
Does oil wear out?
- Thread starter Ray H
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Engine design is a primary factory. Something like the Buick 3800 Series II used in tests are very easy on oil. If the additives could be replenished and the oil filtered well enough then it could be run a very long time without wearing out.
Some other engines will shear and destroy the oil while there is still plenty of additive and tbn retention. Oil can be severely sheared out of grade quickly, so extended drains may not be realistic in some engines, because the oil is sheared (worn) out.
Some other engines will shear and destroy the oil while there is still plenty of additive and tbn retention. Oil can be severely sheared out of grade quickly, so extended drains may not be realistic in some engines, because the oil is sheared (worn) out.
How do you determine the oil has been beaten? Oxidation and viscosity changes are usually the result of contamination and VIIs breaking down.
VIIs can break down, additives can be depleted, contaminants can change the characteristics of the oil, but the oil is still oil is it not?
-T
Oil analysis. UOA.
That Ford engineer that ran his Lincoln for 100,000 miles without an oil change back in the late 60's to early 70's had the oil analized as oftem as most people were doing oil changes.
Back then an oil change with "quality"? dino oil was less expensive than an oil analysis.
Below is a post from another forum which raises intersting questions re short oil changes but does not consider esters
Extended oil life reduces damage to Engines during cold starting:
If all the parameters are kept within allowable limits, oil which has been used for 2000 hours is certainly better than oil used for 200 hours . It is an established fact that maximum damage to any engine occurs at the time of cold starting when all the parts have started movement ,but the lube oil has not reached there ,will reach after a few seconds. After the engine is shut down, every drop of engine oil comes down to sump within a few hours, and when engine has been restarted cold again, many parts make movements in dry condition waiting for the lube oil to arrive there.
When the oil is new , it has both weak and strong molecules, the more the oil is used, the more these weaker molecules get oxidised. When the oil becomes very old, the proportion of strong molecules becomes almost 80%and more and the adhesive power of oil increases, the strength of oil film oil increases. Thats why when the oil is old more than normal drain out period, i.e.2000 hours old, it sticks to every nook and corner of the engine for more than 72 hours. So at the time of cold starting, oil is present everywhere and damage to engine is least . Thats why 2000 hours old oil is better than 200 hours old oil. If you want to enhance the life of engine, extend the drain out period of engine oil to the extent of NO MORE CHANGE OF OIL, yes, but with some device you have to keep all the parameters of oil within allowable limits.
Extended oil life reduces damage to Engines during cold starting:
If all the parameters are kept within allowable limits, oil which has been used for 2000 hours is certainly better than oil used for 200 hours . It is an established fact that maximum damage to any engine occurs at the time of cold starting when all the parts have started movement ,but the lube oil has not reached there ,will reach after a few seconds. After the engine is shut down, every drop of engine oil comes down to sump within a few hours, and when engine has been restarted cold again, many parts make movements in dry condition waiting for the lube oil to arrive there.
When the oil is new , it has both weak and strong molecules, the more the oil is used, the more these weaker molecules get oxidised. When the oil becomes very old, the proportion of strong molecules becomes almost 80%and more and the adhesive power of oil increases, the strength of oil film oil increases. Thats why when the oil is old more than normal drain out period, i.e.2000 hours old, it sticks to every nook and corner of the engine for more than 72 hours. So at the time of cold starting, oil is present everywhere and damage to engine is least . Thats why 2000 hours old oil is better than 200 hours old oil. If you want to enhance the life of engine, extend the drain out period of engine oil to the extent of NO MORE CHANGE OF OIL, yes, but with some device you have to keep all the parameters of oil within allowable limits.
oil never wears out its the additives that do.
Even if oil shears, it can still be recycled. It does not become useless material.
Yep, you're right - the base lube stocks can be hydrotreated to reform to desirable chain lengths, and oxidative double bonds broken and re-saturated with hydrogen. But, in its sheared back and partially oxidized state, it's also of decreased or outrightly marginal lube value (depending on how badly it's been beaten by over-extended drain intervals) until it's re-refined through hydrotreating. Used motor oil is not the same as crude out of the ground, but it can nevertheless be treated with the same processes to effectively restore its purity and lube qualities. I'm speaking of the paraffin lube molecules in Group I, Group II, and Group III base lube stocks, NOT whatever's in the additive pack that's also been consumed or molecularly altered. Once the engine's done its worst to the motor oil, you can filter 'til the cows come home through toilet paper, microfibers, or whatever, even replenish additve, and the results may even look "like-new" clear, but the partially spent base stock's effectiveness is still just as compromised as it was before the trip through the fancy filter - little different conceptually than the simple filtration practiced on pumped crude in the early '20s. You "oil-doesn't-wear-out" guys want something like that circulating through your modern, close tolerance engines with a hit-or-miss OTC additive poured in? Really?
(For my ride, I'd sooner take my chances with ST 10W-30 and an ST filter changed out every 3,000 miles.
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What happens to the oil in our vehicles? Does it wear out,or just get dirty? I'm reading a thread on another site and a common theme is that oil will never wear out or break down,it just gets dirty and thats why we change it out. IIRC from reading this site oil in fact does wear out and break down,am I right?
I'm not an expert, but if you peruse the used oil analyses here, you'll see how oils [over time] lose their original viscosity. That, to me, is part of "wearing out". Of course it does get dirty and fuel diluted in some cases over time.
I'm unsure about what happens to the additive packages over time, but if you compare VOA's to UOA's on the same oils, you should get some idea what happens to those chemicals.
I'm unsure about what happens to the additive packages over time, but if you compare VOA's to UOA's on the same oils, you should get some idea what happens to those chemicals.
Oil does not wear out. However, the additives breakdown over time.
I guess there are a lot of ways to look at things, but I can't agree with the idea that using oxidized oil at 2000 hours makes less wear.
Oils that shear down in the first 100 to 200 hours (we have several here) should be changed by then, and analysis shows high wear at that point. Continuing to use them until they build viscosity at 300 hours continues to do damage to the engine with increased wear. Oxidized oil is decomposition into non-lubriating substances.
Additives are consumed, oil is oxidized, nitration is formed, etc.
Maybe oil doesn't wear out, but every hour of use takes it closer to the point where it does not protect the way it once did.
Oils that shear down in the first 100 to 200 hours (we have several here) should be changed by then, and analysis shows high wear at that point. Continuing to use them until they build viscosity at 300 hours continues to do damage to the engine with increased wear. Oxidized oil is decomposition into non-lubriating substances.
Additives are consumed, oil is oxidized, nitration is formed, etc.
Maybe oil doesn't wear out, but every hour of use takes it closer to the point where it does not protect the way it once did.
Yes, oil "wears out" -and- gets dirty. Note that I think that "oil wear out" includes the effects of contaminates that chemically attack the oil. Also, from my consumer viewpoint, you cannot separate the base oil from the additives. If whatever is in the oil bottle when new "breaks-down" after some time in an engine such that it will not pass the same tests as new oil, then that oil has experienced "wear".
Common sense --> What other substance can you think of that is exposed to an engine environment (temp-cycle, cam-lobe pressures, contaminates, etc) that does not "wear out" over time? Even the engine's metal parts wear out eventually. The key is that whatever the engine is made of and whatever fluids are in it should wear-out slowly and gracefully so that proper maintenance can extend the service life.
There are a lot of definition-of-terms that we must agree upon to have a truly meaningful discussion about this topic - e.g. - define "wear". However, note that it doesn't matter in a practical sense --> if it was possible for oil to only get dirty without "wear", then you and I would still have to change it periodically.
Common sense --> What other substance can you think of that is exposed to an engine environment (temp-cycle, cam-lobe pressures, contaminates, etc) that does not "wear out" over time? Even the engine's metal parts wear out eventually. The key is that whatever the engine is made of and whatever fluids are in it should wear-out slowly and gracefully so that proper maintenance can extend the service life.
There are a lot of definition-of-terms that we must agree upon to have a truly meaningful discussion about this topic - e.g. - define "wear". However, note that it doesn't matter in a practical sense --> if it was possible for oil to only get dirty without "wear", then you and I would still have to change it periodically.
Is there any truth to this at all? Seems like total BS to me. Yea, leave your oil in long enough so it turns to thick tar, so then you'll have minimum drain down after your engine's shut off, and you'll get maximum start-up protection?
I have seen a few engines here that have caused Mobil 1 10w-30 to shear out of grade pretty quickly. This is very unusual. I don't think it has any VII at all, TBN is still good and major fuel dilution has not caused this. I have to conclude that even Mobil 1 10W-30 can be sheared out of grade.
I can only conclude that the PAO basestock itself must shear under extreme conditions.
I have seen a few engines here that have caused Mobil 1 10w-30 to shear out of grade pretty quickly. This is very unusual. I don't think it has any VII at all, TBN is still good and major fuel dilution has not caused this. I have to conclude that even Mobil 1 10W-30 can be sheared out of grade.
I can only conclude that the PAO basestock itself must shear under extreme conditions. [/QB][/QUOTE]
Can you elaborate a little...I would like to know what engines are able to do this, and what it is about those engines that enable them to do the shearing, and at what duration on the oil. I am very curious.
[ November 30, 2004, 02:55 PM: Message edited by: Jakebrake ]
Can you elaborate a little...I would like to know what engines are able to do this, and what it is about those engines that enable them to do the shearing, and at what duration on the oil. I am very curious. [/QB][/QUOTE]
I don't have the time today to research, but hopefully Motorbike will chime in. I know he has a 3 qt. sump and sees this.
Reduced sump capacities, higher operating temps, and gear driven cams might all contribute.
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