Curious as to the depleted ZDDP levels after normal mileage from oil analysis results. What numbers have you seen? In other words, are you seeing drastic depletion or minimal?
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ZDDP level change after oil analysis
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Trying to get a sense of just how much of the ZDDP additive is actually being utilized overall.
You don't see ZDDP depletion in UOAs. There's no concrete reason why it doesn't deplete considering it is a sacrificial additive. Speaking with a retired chemist who made ZDDP for decades, he didn't know why either. It's one of those mysteries of lubricants that's yet to be solved. There are a few theories. My own personal theory is that elements of zinc, phosphorus, and sulfur get kicked back in circulation as old anti-wear tribofilms are replaced or replenished, and also from attachment to other particles in the oil.
The reason we see a depletion with boron is likely due to capture by the filter. Boron in engine oil is typically from a liquid analog of solid particle boric acid which can agglomerate. As it does so, it gets captured in the filter. In the UOA, it shows a steady depletion of boron, but if you were to analyze the filter media, you would likely see boron increasing proportional to depletion in the UOA.
The reason we see a depletion with boron is likely due to capture by the filter. Boron in engine oil is typically from a liquid analog of solid particle boric acid which can agglomerate. As it does so, it gets captured in the filter. In the UOA, it shows a steady depletion of boron, but if you were to analyze the filter media, you would likely see boron increasing proportional to depletion in the UOA.
So, the consensus is that more ZDDP content in oil does not equate to more protection...only takes longer to deplete?
No. A higher ZDDP concentration will result in thicker anti-wear films. Different types of ZDDP form different film thicknesses as well. The greater the shear force in boundary lubrication (ie: aftermarket flat tappet cams/lifters), the thicker the anti-wear tribofilm needs to be to carry the load and prevent excessive wear. That thicker anti-wear film is accomplished with a higher ZDDP concentration and/or a more reactive type of ZDDP.
The type of ZDDP has more to do with how long it takes to deplete. More reactive branched secondary alkyl ZDDPs produce thick anti-wear films very quickly but also deplete very quickly. These are commonly found in break-in oils and some high end racing oils. The opposite end of the spectrum would be a linear chained primary alkyl ZDDP that has poor reactivity and low anti-wear film establishment but lasts a very long time. This is commonly found in some HDMOs though blended with a small amount of secondary alkyl ZDDP to give some reactivity. Below is an example of the rate of anti-wear film establishment between a branched secondary alkyl ZDDP (2-butanol) and a linear primary alkyl ZDDP (1-dodecanol).
The type of ZDDP in most all PCMOs, including Euro oils and some racing oils, is a 70/30 blended primary/secondary alkyl ZDDP additive.
What got me thinking about this is the science behind it particularly. The following report seems to contradict generally held conceptions... https://www.sciencedirect.com/science/article/pii/S0301679X19303214
What exactly is the accepted/optimal thickness and who made this determination? This is the only study I have found to date that addresses this.
What exactly is the accepted/optimal thickness and who made this determination? This is the only study I have found to date that addresses this.
ZDDP is sacrificial, zinc isn't. The instrumentation used for UOAs only sees zinc. It can't differentiate whether the zinc is from ZDDP or ZnCl. The compounds in the sample are broken down into their individual atoms in the plasma. The instrument is tuned to see the wavelength of light emitted by Zn when an electron is kicked up an energy level by the heat of the plasma. The original source of the zinc can't be determined.
You are essentially correct on why the values don't change much. The tribofilm is in a constant state of flux being formed and "used up" at the same time. Each time the tribofilm is called into action the ZDDP molecule is broken down into smaller and smaller pieces until they are no longer functional anti-wear compounds. The ratio of functional to non-functional Zn compounds changes as the oil ages. If the oil is run too long there are not enough functional compounds to form an effective tribofilm. The concentration of Zn in the oil remains about the same, with any difference due to dilution/concentration of the oil or analytical error.
Ed
That article is referring to micro-pitting from high ZDDP concentrations. Unfortunately, there's no such thing as a free lunch. Micropitting is a form of localized corrosion. ZDDP is an acidic ester and that acidity can give way to corrosion at high concentrations. Different types of ZDDP can cause this at different concentrations, but many variables that aren't addressed in that article. (as it would it turn into a novel trying to explain them all) The corrosive effects will be different in a fully formulated oil, with detergents, anti-oxidants, etc..., than it will in a base oil by itself, especially in a base oil with poor solubility such as PAO. That article doesn't mention any ester added to the PAO for solubility, which has me curious about it. I remember reading that article a while back, but I'll have to go through it again.
The optimum thickness varies depending on the application. You need sufficient film thickness to match or exceed the surface roughness to reduce the contact of micro-asperities between the two parts. Then there's shear forces such as a flat tappet lifter spinning on a slanted cam lobe. The temperature of the oil plays a factor. The type of metal is another factor.
The optimum thickness varies depending on the application. You need sufficient film thickness to match or exceed the surface roughness to reduce the contact of micro-asperities between the two parts. Then there's shear forces such as a flat tappet lifter spinning on a slanted cam lobe. The temperature of the oil plays a factor. The type of metal is another factor.
I know how an ICP works. I probably should've said "You don't see zinc, phosphorus, and sulfur deplete in UOAs." You don't see zinc from anything else in engine oils besides ZDDP so I figured the point would come across without having to break that all down. The "zinc" is just a neutralizing carrier for the molecule anyway. The phosphorus and sulfur provide the wear protection. It starts off as phosphorus pentasulfide, then reacted with various alcohols to make dialkyldithiophosphoric acid which is then neutralized (to a varying degree) with zinc oxide to form zinc dialkyl dithio phosphate.
So, short story is that there is nothing concrete to substantiate claims that more ppm of ZDDP is providing greater protection?
There's tons of evidence to support that a higher concentration of ZDDP provides better wear protection when called for. If the engine has no use for the greater film thickness, then the higher concentration will be of no benefit. The (keyword) potential for more wear protection is there when demanded. Engines that need the thicker anti-wear films can make use of the higher concentration.
As far as the corrosion is concerned, it's... well, not a concern. The only time you really have to worry about that is when you're getting into the 2000+ ppm range. You can recreate the micropitting easier with an MTM and lone ZDDP additive at a lower concentration, but in an engine, it's not a major concern as you have other additives that are combating that corrosion. Above ~2000 ppm is where the corrosive wear begins to cancel out the abrasive wear prevented. Besides, there's no application on Earth (outside of break-in) that needs more than ~1500 ppm. Even dwell nosed solid flat tappet super stockers with really steep ramps and 500+ lbs spring pressure on the nose are just fine on 1300-1400 ppm. The only reason brands put >1500 ppm in an oil is for advertising/marketing to the gullible populace that think more is always better.
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Link to those "tons" if generally available. I'm speaking of average Joe's ability to cypher which oil he genuinely needs for a given application.
Funny how you brought up Super Stocker's...many of us in the Stock Eliminator ranks run modern full synthetic oils with no problems. Quaker State 5W30 full synthetic in mine...zero additives btw.
Funny how you brought up Super Stocker's...many of us in the Stock Eliminator ranks run modern full synthetic oils with no problems. Quaker State 5W30 full synthetic in mine...zero additives btw.
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Boundary Friction of ZDDP Tribofilms
Film Thickness and Friction of ZDDP Tribofilms
The Mechanism of ZDDP Antiwear Film Formation
The History and Mechanisms of ZDDP
There's just a few of many. Hugh Spikes is credited in many of the white papers involving ZDDP. He's a master of his craft and legend among tribologists. Anything he states, you can take to the bank.
Interesting reads, but none of these really answer the question of what is actually required for our engines. The average consumer still has no reliable information other than someone's statement such as "I've never had a failure using brand X"...not really compelling or helpful.
I believe the link I provided shed more light on the properties, formations and behavior of ZDDP than any I have seen to date. The question of just how much ZDDP is required remains unanswered and unavailable to the average Joe. I would have liked to see some similar tests carried out with consumer available oils, but I understand this is a costly and time consuming process.
You do have the wear protection that's guaranteed by many manufacturer approvals. Most of the European ones have stringent wear requirements.
Sorry, but I have no knowledge of any oil manufacturer replacing a toasted engine. I would prefer some real world testing over a symbol or label on a bottle.
Uhh, approvals and the tests in SAE J300 are real world. What would you suggest instead?
Those are nothing more than tests for specific properties just as described in the above links...exercises in science if you will. That does nothing to describe the outcome of a specific oil for you or I. According to the general consensus My Stock Eliminator engine should be in shambles from it's paltry oil ZDDP content.
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