used oil better than new?

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SAE paper 2007-01-4133 https://shop.sae.org/technical/papers/2007-01-4133 Lower friction in old vs new oil. That would explain the initial high wear with new oil phenomenon. I bet this is because ZDDP needs to be heated first to activate. My thoughts: should there be a market for a "preowned oil" and should we break in engines every time we change oil? ;\) Abstract: Engine oils are subjected to a series of industry standard engine dynamometer tests to measure their wear protection capability, sludge and varnish formation tendencies, and fuel efficiency among several other performance attributes before they are approved for use in customer engines. However, these performance attributes are measured at the end of tests and therefore, do not provide any information on how the properties have changed during the tests. In one of our previous studies it was observed that engine oil samples collected from fleet vehicles after 12,000 mile drain interval showed 10-15% lower friction and more importantly, an order of magnitude lower wear rate than those of fresh oils. It was also observed that the composition of the tribochemical films formed was quite different on the surface tested with the drain oils from those formed with fresh oils. The objective of this investigation is to demonstrate how the friction and wear performance changed with oil drain intervals. A fleet of three vehicles was run in Las Vegas and oil samples were collected at various drain intervals from 3,000 miles to 15,000 miles. As in the previous study, the results showed that the aged engine oils provide lower friction and much improved wear protection capability. These improvements were observed as early as the 3,000 mile drain interval and continued to the 15,000 mile drain interval. The composition of tribochemical films formed on the surface with the 3,000 mile drain interval is similar to that formed with the 12,000 mile drain interval as seen before. These findings could be an enabler for achieving longer drain interval although several other factors must to be considered.
 
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MolaKule told me that fresh oil ZDDP takes awhile to bond to the engine. So frequent short oil changes would increase wear.
 
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I wonder how many engine hours are customary to reach this critical point? if the average speed is 60 mph that is only 50 hours. If the average speed is only 20 that is 150 hours. I have read that 200 hours of operational temperature running gets the oil broken in. THis makes sense as the formulators have to aim to pass several tough tests on aged oil.
 
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 Originally Posted By: Dr_No
MolaKule told me that fresh oil ZDDP takes awhile to bond to the engine. So frequent short oil changes would increase wear.
Did he also tell you he was the Man in the Moon
 
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For sure...oil that's contaminated with metals, silicon, fuel and moisture would surely lubricate better. So, why are we changing our oil at all??
 
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 Originally Posted By: Dr_No
MolaKule told me that fresh oil ZDDP takes awhile to bond to the engine. So frequent short oil changes would increase wear.
What about the zinc from the old oil that has bonded?
 
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I don't think the new oil and the old oil sign non compete agreements ;\) ... The new oil has the more aggressive/reactive chemistry and displaces the old oil's additives from the surfaces.
 

friendly_jacek

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 Originally Posted By: Steve S
What about the zinc from the old oil that has bonded?
The top layer produced by ZDDP is sacrificial, it is stripped away with friction. The new oil may not have ZDDP activated yet to produce a new layer.
 

MolaKule

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 Quote:
These findings could be an enabler for achieving longer drain interval although several other factors must to be considered.
There's the clincher, "could.. and "other factors." My theory is the older oil thickens up and certain polymers that are formed act to increase film thickness, but there IS a limit here. You may see increased wear after the 12,000 mile figure due to other additives being depleted. BTW, ZDDP only takes a little heat and pressure to form tribofilms on the surface. And as others have stated, the old zddp doesn't disappear entirely.
 
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 Originally Posted By: MolaKule
 Quote:
These findings could be an enabler for achieving longer drain interval although several other factors must to be considered.
There's the clincher, "could.. and "other factors." My theory is the older oil thickens up and certain polymers that are formed act to increase film thickness, but there IS a limit here. You may see increased wear after the 12,000 mile figure due to other additives being depleted. BTW, ZDDP only takes a little heat and pressure to form tribofilms on the surface. And as others have stated, the old zddp doesn't disappear entirely.
Somewhere on this board I think it was you or Bruce that had stated a theory as to why higher wear metals showed up in UOA's with recently changed fresh oil. It actually made a lot of sense at the time, and you/he had mentioned you didn't believe it was wear. Wish I could find that thread, 30 minutes of searching left me without finding it. Do you recall the thread? If so do you have a way of finding it? TIA Frank D
 

friendly_jacek

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We knew for a long time that the first 1000 miles had the highest wear particle concentration. Various people had various opinions or speculations why. In this study, it was shown that not only wear but also friction increases with new oil. Below is a link to a free, full length paper by the same authors with more details: http://findarticles.com/p/articles/mi_qa5322/is_200711/ai_n21298415/ Very good reading. Sounds like a significant ZDDP decomposition is needed for the effect to kick in. Also, it took 25hrs to build up the thickness of tribofilms on new surfaces (1500 miles of driving at 60 mph). That is prolonged if new oil is used. I'm glad I drive gently in the first 1000 miles in new cars I own. This should debunk the myth of frequent oil changes during brake in. I bet this is why Honda insists on keeping the oil in for the full OCI during brake in.
 
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As I mentioned buried somewhere on this site a very well respected member commented on this very topic. IIRC it had nothing to do with increased wear from fresh oil. I wish I could find it, or remember his reason, but it made a lot of sense! It might have something to do with the fresh add pack is freeing up dirt and junk, which in time gets trapped in the filter. But early on the #'s are high because of the fresh oil cleaning and freeing up junk. Wish I could find the post!!!!!!!!!!!!!!!!!!!!!
 
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that is what Ford and conoco say, oil is at its best after 3k...carbon buildup i think
 
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Yea but is it freeing up junk when fresh, and that junk contains residual metals being released? So in effect it's not additional wear, it's just junk that was freed up? That makes sense to me. AD
 

friendly_jacek

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 Originally Posted By: demarpaint
As I mentioned buried somewhere on this site a very well respected member commented on this very topic. IIRC it had nothing to do with increased wear from fresh oil. I wish I could find it, or remember his reason, but it made a lot of sense!
It may be just me, but I prefer science and empiric evidence rather than what a BITOG member says or thinks. Especially since BITOG is moderated by people with no tribology experience, but with personal agendas.
 
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The member IIRC was a Tribologist (sp), most others comments I take with a grain of salt.
 
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There are tribologist that post on a regular basis. I trust that I will get the best information here due to the fact that the members here study oils and additives even if it is not their chosen field for employment. Thank you to all the members that help me take care of all my vehicles. Helen
 
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 Originally Posted By: friendly_jacek
 Originally Posted By: demarpaint
As I mentioned buried somewhere on this site a very well respected member commented on this very topic. IIRC it had nothing to do with increased wear from fresh oil. I wish I could find it, or remember his reason, but it made a lot of sense!
It may be just me, but I prefer science and empiric evidence rather than what a BITOG member says or thinks. Especially since BITOG is moderated by people with no tribology experience, but with personal agendas.
That's a broad brush you are painting with there Not So Friendly_Jacek. Your expertise is welcome and will be appreciated if presented in a more civil manner. Ad hominum and ad hominems attacks can result in a ban. Please avoid them.
 
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