Should I leave a little used oil in? ( DNewton3 )

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Prolly true, but ...

Back in the day when I was wrenching for a living, I saw a fair number of cars and trucks with "well developed" oil come through the shop. They always seemed to run well and I know that many of them lasted a long time. I'd see them running years later with the original engine. So there is something to this ...

This thread is about leaving oil in place. I know it got off the rails a bit, but still good info here.

As long as the oil and conditions are not forming excessive varnish or sludge, leaving it in place is a not a bad thing for wear
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Originally Posted By: BrocLuno
Prolly true, but ...

Back in the day when I was wrenching for a living, I saw a fair number of cars and trucks with "well developed" oil come through the shop. They always seemed to run well and I know that many of them lasted a long time. I'd see them running years later with the original engine. So there is something to this ...

This thread is about leaving oil in place. I know it got off the rails a bit, but still good info here.

As long as the oil and conditions are not forming excessive varnish or sludge, leaving it in place is a not a bad thing for wear
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And the SAE study acknowledged that very thing:
"These findings could be an enabler for achieving longer drain interval although several other factors must to be considered." (note I quoted them fully including grammatical error)
IOW - they admit that wear rates are not the only thing to consider when extending OCIs.
Of note, and reasonable concern, would be soot/oxidation.
But guess what? Those things can ALSO be tracked in a UOA. If your soot/ox (aka insolubles) are low, then where's the concern? In fact, if one is to anally inclined, he/she can pop off a valve cover and take a look-see! If soot/ox is not visually present, and it's not showing up in the UOA, then where' the risk??????? I have NEVER advocated for the blind extensions of OCIs. What I tell folks to do is pay attention to the data they pay for. If your wear rates are low, and your contamination is low (indicating a healthy system), then extended OCIs make sense. In an engine that is "healthy" (low contamination from particulate, no coolant, no excess fuel, etc), if you have low wear rates, and the other intrusions are low or non-existent, then why not extend the OCI? It's not like we cannot reason our way through this ... Are there things to watch for? Sure. But if they are in control, why not extend?

People so very frequently pay for a UOA, and then promptly ignore the data and continue down their wasteful course.
 
Well there is different kinds of waste. You say folks are throwing away good fluids. But we recycle nearly all our fluids, so there is no real "waste". If I do a short OCI, it is usually because I was under the vehicle anyway doing something else and it's a handy time to get this out of the way.

On the flip side, I ran my BBC 3/4 ton truck 5 years w/o changing the oil and filter because it rarely saw more then 2,000 miles a year. I had the valve covers off for a leak and all looked good. The oil was dark, that's it. After the fifth spring, I decided that was enough. NO UOA as I knew it was thickening, so I changed it. Now it's someone else issue
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The Saab is a different beast. Due to a design fault, the front CAT is right next to the pan at the oil pick-up point. In stop and go traffic it will coke so bad that it will eventually starve the whole engine for oil. The way to beat it w/o doing a pan drop is to run active add pak synthetic oils and change often. I toss a 1/2 can of BG 109 in for extra measure. The pan was off at 100,000 when the car got a new clutch per recommended inspection interval. Clean enough. This is not an ongoing wear related issue, but it does drive OCI's.

So there is potential waste in time or money related to OCI's that are not necessarily wear related or only tangentially oil chemistry related ...
 
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As engine oils age, they become thicker and that results in a loss of fuel economy from increased fluid friction in the crankshaft and connecting rod bearings.
There is mention of the oil increasing two steps out of grade, which would be from xW20 to xW40.
We can throw out any expectations of cold cranking, pumping and flow beyond the half way mark in this SAE paper, or around 7,500 miles.
The friction loses or gains on 12 flat tappet cam lobes will not impact fuel economy, but thicker oil definitely will.
Shall we now study effect and consequence of aged oil in repeated cold start wear in northern Minnesota instead of taxi service in los Vegas?
My take on this issue, is the loss of fuel economy from aged engine far outweighs the savings of extended drains.
How did this experiment with overly extended oil drain affect other engine component wear, particularly in the ring zone and top ring turn around point?
Not measured, documented, or included as total engine wear was not the scope of the test, but instead a study of film formation on flat tappet cam lobes in a mild application in taxi service.
Hardly a case for extended drain intervals.
What a joke!
 
I think the points you mention are the only real benefit from moving from a quality dino oil to a synthetic. Seems they may not thicken as much, so can handle longer drain intervals...

But, that's not what most folks do with syn's. They claim better lubrication (no proof I've found ...), better cold starts and cold flow (I agree on starts, flow is a nonsense-issue), and better heat resistance (that's the part about not thickening). But, they still change them early ...

For my Saab, there's a reason. For most cars - not ...
 
Originally Posted By: userfriendly
As engine oils age, they become thicker and that results in a loss of fuel economy from increased fluid friction in the crankshaft and connecting rod bearings.
There is mention of the oil increasing two steps out of grade, which would be from xW20 to xW40.
We can throw out any expectations of cold cranking, pumping and flow beyond the half way mark in this SAE paper, or around 7,500 miles.
The friction loses or gains on 12 flat tappet cam lobes will not impact fuel economy, but thicker oil definitely will.
Shall we now study effect and consequence of aged oil in repeated cold start wear in northern Minnesota instead of taxi service in los Vegas?
My take on this issue, is the loss of fuel economy from aged engine far outweighs the savings of extended drains.
How did this experiment with overly extended oil drain affect other engine component wear, particularly in the ring zone and top ring turn around point?
Not measured, documented, or included as total engine wear was not the scope of the test, but instead a study of film formation on flat tappet cam lobes in a mild application in taxi service.
Hardly a case for extended drain intervals.
What a joke!


As for vis causing a film induced drag, the SAE study did not study that issue at the rings, but it does study it at the cam lobes. And guess what - it shows a friction DECREASE as the TCB matures, despite the fact that vis thickens. As the TCB gets "better" and firmly established, not only does the wear go down, but also the frictional drag at the lobe/tappet interface. They hooked up a torque meter to thae cam lobe drive and measured the force; the older the oil got the less drag it had. All this while the vis thickened. So the thicker oil did not hurt with power loss nearly as much as the reduced friction helped.

I will note here the grand dichotomy in mentality of some here (not necessarily you, but many others here) regarding vis. On the one hand, they would decry the thickening of a vis due to OCI extension. But OTOH, they would also decry the use of thin oils, because the vast majority of folks still think "thicker is better". So, why is it that a 20 grade that thickens to a 30 or 40 grade will be a concern for fuel economy, but using a 30 grade or a 40 grade to start with is somehow "better" and the loss of fuel economy is now deemed as a tolerable side effect? This just reeks of a two-faced approach to vis and fuel consumption! If one is willing to tolerate a fuel economy loss by running a 30 grade, then why does it matter of that 30 grade came out of the bottle that way, or thickened that way? Just pure hypocrisy!

You can concern yourself with cold starts in MN, but frankly you'll never be able to tell how much fuel a thicker lube would consume because the VAST majority of the fuel consumed in a cold start is due to the enrichment of the fuel stream to keep the engine running for the first several minutes (like a choke in the old days of carbs). While a thicker vis may cause a minor loss of fuel economy, it will pale in comparison to the very rich fuel injection (or carb) sequence until the engine warms up. And once the engine is warm, so goes the oil. Sorry, but I don't buy this as being a major issue; it's a stretch to make a mountain out of this mole-hill.

While you could certainly state that the SAE study does not address the issues of wear in other areas ... My macro data study most certainly does. The UOA data does not discriminate as to the origin of wear. It's all in the fluid stream. And yet 15,000 UOAs tell us that wear rates drop as the OCI increases. Cam lobes, rings, cylinder walls, main and rod journal bearings, cam chains; it's all in there. And all that concern still manifests into .... well, nothing. The wear rates drop as the OCI goes on. The SAE study does a good job of describing WHY we can believe the TCB is the main controller of wear. It's not vis; vis does not affect wear. The study shows it and my data shows that. It's not FP, or acid/base, or other things. While many of these may be minor contributors, they are not the main contributor; that's the TCB.


Many of you are full of Yabuts. (Yeah, but ...) And they don't amount to much of anything. I realize it's hard to let go of preconceived notions, but the reality is that moderate extensions of OCIs is perfectly OK, and pays a dividend that other patterns can never do. This isn't a unique situation for only a few exmaples. It's 15,000 UOAs from all over North America. It's car that drive easy, SUV soccer moms, police cars, trucks that haul excavators, semi's that haul food, it's stationary generators, and it's tractors in the field. It's all these engines in the heat of AZ, the humidity of FL, the cold of MN, the moisture of the northwest. It's hard drivers and old folks. It's grain trucks in dusty field. It's stop/go cycles and steady state highway service. It's fuel from a huge variety of sources. It's dinos and syns. It is, in a nutshell, the blend of life that is our daily lives. The fact is that ALL ENGINES with healthy operating parameters experience the phenomenon of lower wear rates with OCI extension. Sorry if this fact makes your sleep more difficult.

So frankly I find your concerns a non-issue.
 
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Originally Posted By: dnewton3
You can concern yourself with cold starts in MN, but frankly you'll never be able to tell how much fuel a thicker lube would consume because the VAST majority of the fuel consumed in a cold start is due to the enrichment of the fuel stream to keep the engine running for the first several minutes (like a choke in the old days of carbueration). While a thicker vis may cause a minor loss of fuel economy, it will pale in comparison to the very rich fuel injection (or carb) sequence until the engine warms up. And once the engine is warm, so goes the oil. Sorry, but I don't buy this as being a major issue; it's a stretch to make a mountain out of this mole-hill.


Nah, not even close Dave...although if you've got some EVIDENCE that it's all enrichment, then please bring it to the table, rather than blowing off valid points as irrelevant.

Here's the power required to overcome viscous friction as an engine warms...clearly, as the viscosity drops through warming, the wasted energy goes down...
warmup.jpg


And clearly, viscosity increase increases the lost energy in areas that undergo hydrodynamic lubrication. As can be seen here...the power loss in a bearing can easily be doubled with a few changes in grade...it's the whole premise of low viscosity oils for fuel economy.

moft%20viscosity.jpg


The vast majority of frictional losses inside an engine are due to viscous drag in the hydrodynamic regime...pistons and bearings ARE elated to viscosity.

Cam wear, which has been known for over 100 years to be additive not viscosity dependent is viscosity insensitve.

Cam frictional losses are similarly viscosity insensitive.

But to conclude that because you favourite paper demonstrates lower cam drag with the tribofilm formed by more degraded oil applies to the whole of the engine is ludicrous, and demonstrates an absolute lack of understanding in what an engine IS, let alone lubrication regimes...

So frankly, I beleive that you are being either disingenuous, or displaying your lack of understanding.

(will touch on UOA later)
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Edit...oooh, you've got that edit thing going again...nice.
 
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Originally Posted By: BrocLuno
Well there is different kinds of waste. You say folks are throwing away good fluids. But we recycle nearly all our fluids, so there is no real "waste". If I do a short OCI, it is usually because I was under the vehicle anyway doing something else and it's a handy time to get this out of the way.


Well, we all pay for the oil we get in the bottle, but none of us are paid for the oil we dump into a recycling container. While I do understand your overall concept, it does not put money into MY pocket. Therefore, the manner in which I can double my money is to double my OCI. If I OCI every 10k miles rather than 5k miles, I save on a factor of 2x! I have no concern of how much money some recycler makes on my lube once it goes into their tote. I don't make any money back on their collection of used oil. By cutting my waste in half, I have doubled my money. Something the lube recycle facility will never pay me for.

And by all means, some folks like to double down on their waste by paying for UOAs and them ignoring the data. That's waste heaped upon waste.
 
Originally Posted By: Shannow
Nah, not even close Dave...although if you've got some EVIDENCE that it's all enrichment, then please bring it to the table, rather than blowing off valid points as irrelevant.


My experiences are both localized, and regional.

Cold engines (the first few minutes) consume FAR more fuel than what a vis shift is going to apply.

In winter, my MPG will go down about 2 MPG due to the fuel enrichment curve. In summer, it jumps up. During those times, I've had both thick and thin lubes in use, so there is no correlation to the vis nearly as much as the fuel curve.

This was also seen in our fleet of vehicles operating inside/outside at the Ford plant I worked at. The cold temps altered fuel economy far more than any vis ever did.

I will research this some more later tomorrow when I get a chance.
 
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Some of that winter/summer mpg shift is due to the difference of summer gas, vs winter gas. Winter gas tends to have less energy per unit volume

I do agree that engines run a rich mixture until warmed enough to enter closed loop operation.
 
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Originally Posted By: Shannow
The vast majority of frictional losses inside an engine are due to viscous drag in the hydrodynamic regime...pistons and bearings ARE elated to viscosity.

Cam wear, which has been known for over 100 years to be additive not viscosity dependent is viscosity insensitve.

Cam frictional losses are similarly viscosity insensitive.

But to conclude that because you favourite paper demonstrates lower cam drag with the tribofilm formed by more degraded oil applies to the whole of the engine is ludicrous, and demonstrates an absolute lack of understanding in what an engine IS, let alone lubrication regimes...

So frankly, I beleive that you are being either disingenuous, or displaying your lack of understanding.



I agree with you here. The SAE study we speak about even addresses the fact that they only did valve train wear and frictional loss, and that other sources will be more. And I agree with that.

But how deep down the rabbit hole are we going to go here? Again - I am not concerned about a minor fuel economy loss due to slightly thicker lube (often up to a grade that other folks choose straight out of the bottle, I remind you). What I am more concerned about is a safe extension of OCI to get value in the bottle. It's easy to see I can get anywhere from a 5x to 3x gain, depending upon how one would look at the origin of OCI; a 3k mile OCI extended to 15k miles is ONE FITTH the oil purchased, and still getting very desirable wear rates across the entire engine.

I find it ironic that folks (not necessarily you, becaues I don't follow your vehicle and UOAs personally) will concern themselves with a "thicker is better" mentality when it comes out of the bottle, but it's somehow objectionable if it happend in the engine. Pumping loss is pumping loss, regardles how the lube got to that state. I could even argue that staring with a thinner lube at least gains some form of savings when the lube starts thin, contrasted to someone who would pick a 40 grade right off the shelf. And those are often the same folks that would tell me they want their ride to last a LONG time, and are willing to pay for upgraded products to make it get there. But somehow they then worry about minor fuel economy losses of a thicker lube? Just plain silly. And hypocritical if you ask me.

The number one controller of fuel economy? That thing at the end of your right leg ... The interaction of your foot and the pedal will control fuel savings FAR more than any concern of a lube that gets a bit thicker due to OCI extension.
 
I think it would be beneficial economically on a large scale if people were more informed.

Many still do 3mo/3000 miles... because the sticker in the windshield tells them to do so.

Just like poorly programmed traffic lights waste millions of gallons of gasoline very year, a huge amount of unnecessary changed oil would be saved... many, many thousands of gallons, every year. You'd think environmentalists would be all over these and other various related issues?

I have 18 engines on my ranch. 4 diesel, 14 gasoline.
I don't want to waste time or oil if I don't have to.
 
I will do more detailed research later, but here's a start:

http://www.fueleconomy.gov/feg/coldweather.shtml

http://www.fueleconomy.gov/feg/factors.shtml

http://www.metrompg.com/posts/winter-mpg.htm

There are a LOT of links to this topic.

And not one of them will quantify the loss due to a vis grade increase. However, it's very fair to say that vis shift is probably a minor issue relative to all the other contributors in these conditions. It's a ghost to chase. I don't think we'll ever be able to quantify it.

Does the thickening matter to fuel economy in winter starts? Yes - probably so. To a tiny degree that just about no one will ever be able to prove.

It's a fools errand to say that cold MN starts within an extended OCI are going to matter to ones wallet, to a manner in which it would be noticed over all the other inputs.

I stand by that.
 
Oil that has thickened 2 grades at 100C has lost all hope of passing a winter grade lower than perhaps 25W.
Who cares about fuel economy if the engine won't crank over, and if it does, better hope that it does not start.
That mud you call engine oil is not going to flow anytime soon lower than about the freezing point.

This SAE paper was preformed with a synthetic 5W20 that went from 8.4 to 15.9 KV100C. Instead, let's do the same experiment with
10W30, run it until it is a SAE 50 something, drive the vehicle to the northern Michigan peninsula in January, and call me in the morning.

Personally I don't give a hoot about the 5% fuel economy I will gain from using a lightweight engine over my thick stuff,
but you won't find my winter grade out to lunch vs ambient.

The discussion here is the economic benefit of extended oil change intervals, not one grade vs another.
If we throw out my bad habits, stick with a friction modified xW20 or xW30, extending OCIs to save engine oil over fuel cost is going to cost you more.

Lastly, at least for now, engine oil is way down the list of the operating cost of a vehicle.
Monthly payments, fuel, insurance, tires and repairs to wear items all come ahead of engine oil and filters.
 
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Originally Posted By: dnewton3

As for vis causing a film induced drag, the SAE study did not study that issue at the rings, but it does study it at the cam lobes. And guess what - it shows a friction DECREASE as the TCB matures, despite the fact that vis thickens. As the TCB gets "better" and firmly established, not only does the wear go down, but also the frictional drag at the lobe/tappet interface. They hooked up a torque meter to thae cam lobe drive and measured the force; the older the oil got the less drag it had. All this while the vis thickened. So the thicker oil did not hurt with power loss nearly as much as the reduced friction helped.


Uh, Dave, This is what the article actually says on page 6, right column, second paragraph:
Originally Posted By: SAE 2007-01-4133
However, it should be noted that valvetrain friction loss is a small portion of the total friction loss in an engine. The majority of frictional losses in an engine come from main bearings, con rod bearings, and piston ring and bore contacts. These contacts mostly operate under hydrodynamic lubrication where frictional losses are governed by the viscosity of the oil (18). In vehicle tests, loss of antioxidancy with oil aging results in an increase in viscosity (13). The frictional increase due to increased viscosity is much larger than the valvetrain friction reduction resulting in a net friction increase.


Ed
 
I'm only going to reply to those issues where I think you are way off base here.

Originally Posted By: dnewton3

The study clearly states that a GF-3 "factory fill", a GF-4 "factory fill" and a prototype GF-5 were used. Sir, factory fill fluids are NOT "non fully formulated", as you claim. They are produced for consumption by the end user and are, in fact, in a state of full add-pack as delivered for use. Additionally, when the study was written, the "prototype" GF-5 has since become the fully-formulated product that is now their offering. It was only a prototype then as they were not yet offering GF-5 yet. But what was "prototype" then is in the bottle now, so ALL THREE LUBES were essentially as one can purchase then and now, and are in fact "fully formulated".


Yes, the SAE article under discussion did use fully formulated motor oils.

The following words are from the quoted articles, not this study. Those articles are using non fully formulated oils to study the effect of the additives individually. This is the source of the mistaken idea that new fully formulated oil removes the existing tribofilm put in place by a fully formulated oil.

Originally Posted By: SAE
Fujita et al. demonstrated that the thickness of the lubricant-derived film increases steadily with test duration and stabilizes at the 50-100 nm level. The thickness is almost independent of phosphorous concentration (2). Film thickness is also dependent on oil temperature with higher temperatures tending to promote greater film thickness (3). However, when a dispersant is added, the film is removed and the film thickness stabilizes at a lower value. The antagonistic behavior of dispersants is well-known and one of the possible mechanisms was believed to be the competition between the dispersant and ZDDP molecules to adsorb on available surface sites.
2. Fujita, H., Glovnea, R.P., and Spikes, H.A., "Study of zinc dialkyldithiophosphate antiwear film formation and removal processes, part I: Experimental", Trib. Trans., 2005, 48, pp.558-566.
3. Taylor, I., Dratva, A, and Spikes, H.A., "Friction and wear behavior of zinc dialkyldithiophosphate additive", Trib. Trans., 2000, 43(3), pp.469-79.

Originally Posted By: Authors of this SAE paper
it points to the fact that once the film is formed with a fully formulated oil, it is not removed very quickly. The existing film may affect the chemical mechanism for forming the new film which provided the reduced friction and wear rate benefit.


Originally Posted By: DNewton3

Close; they ran them to 15k miles; maybe that was a typo on your part?


Yes, as was Cobalt 66. It's Cobalt 56.


Originally Posted By: edhackett
... the new oil was always run on new parts. They had not undergone the break in that valve train parts undergo. The used oil was always run on broken in parts.

Originally Posted By: DNewton3
No sir, that is not correct. Quoting the study:
"A different cam lobe and a tappet shim were used for each oil." Now, the study does not specifically state if the cam and tappets were new or broken-in, but it does CLEARLY state that each lube had a different part-group introduced. To me, the inference I take is that rather than stacking the wear induced from all tests onto the same single cam/tappet, they used a "new" (not brand new, but unique in that each had not been previously utilized in testing) set of parts for each oil. Each time they swapped oils, they set it up with a different lobe/tappet. Whether or not these were "new" (versus broken-in) or not, the variability you infer is not present. Each lube got a unique (and presumably reasonable equal) lobe/tappet set up.


See figure 4, where they refer to the shim used with new oils as "fresh" or "used". The nature of the test would preclude any break-in as the oil used would leave traces of a tribofilm that would interfere with their results. If the intent of the experiment was to evaluate wear, each run of every oil should have been on a "fresh" shim. These were cobalt 56 doped parts and very expensive. Each oil got a shim and rocker. The new oil was always run on the "fresh" shim. Subsequent runs had the benefit of 100 hours of run in from fresh and the residual tribobilm that they stated remained after their cleaning procedure between runs.

Cobalt 56 has a half life of 77.27 days. There would be no used parts kicking around. Two runs of the same oil on the same shim about 2.5 months apart would result in half the wear being observed. Used could be taken as conditioned(broken in) just before use, but see above about not wanting an existing tribofilm.


Originally Posted By: edhackett
The second main uncontrolled variable is that since this was a bench test the new oil was never mixed with the used oil that carries over in an OC or exposed to new combustion byproducts. It remained "virgin" throughout the test, unlike what happens in the day to day operation of an engine.

Originally Posted By: DNewton3
I don't disagree here, but I do question your point? New oil is new oil. As soon as it would be mixed with carry-over (redisual) oil, then it's no longer "new". Each engine (and each person whom maintaines that engine) is going to exhibit a different level of how much residual is left to be mixed into the new oil. That is inescapable. However, residual oil is a bit of an overblown thing. It's unavoidable, and generally harmless.


The point is that the fact that the very thing that makes for a better triboflim is happening in an engine and not on the test bench brings the applicability of the bench test results into question when it comes stating new oil causes more wear in an engine. It's a very very long stretch to make the logical jump that 100 hours of operation without being exposed to normal aging equals 100 hours in an engine. It would appear that not only is the carry-over generally harmless, it appears it could be of benefit.

Ed
 
Here's a discussion that I initiated today on the ACTUAL UOAs of the oils in the engines that they were "aged" in...

https://bobistheoilguy.com/forums/ubbthreads.php/topics/4439092/Re:_3_off_Crown_Vic,_5W20,_Las#Post4439092

When I said that the oils were shagged, you can form your own opinion on what's going on...

To say that the study that is only testing the formation of the tribofilm by the used oil on cam and disks "proves" the efficacy of long oil drain intervals...and looking at the UOAs of the oils in actual service, you can clearly see that the link just isn't there in the quoted paper.
 
Originally Posted By: dnewton3
In winter, my MPG will go down about 2 MPG due to the fuel enrichment curve. In summer, it jumps up. During those times, I've had both thick and thin lubes in use, so there is no correlation to the vis nearly as much as the fuel curve.

One problem with that notion, though, is that say a 10w-30 during a warmup phase isn't ridiculously different from even a 0w-20 during warmup. The big difference is the cold oil versus the warm oil, irrespective of SAE grade.
 
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