ZDDP on cylinder walls and main bearings

[qais90]

Hello, I have a question please, does ZDDP additive protects cylinder walls and main bearings as much as it protects the camshafts??
In another way, is the protecting film on cylinder walls is as thick as on the camshafts??
Because many articles talking about zddp mainly focus on camshafts and lifters,

 

[Cujet]

ZDDP is known to protect rings and cylinders in some cases. How much protection it offers and whether that protection applies to, for example, Nikasil coated bores with chrome or moly faced rings is unknown to me.

Adequate HTHS for hydrodynamic lubrication and ZDDP for protection of sliding parts such as cams, lifters, rings and cylinder liners.

Despite the claims that we have a replacement additive for ZDDP, we really don't. Test after test show it's effectiveness. It's also interesting to note that some tests show ZDDP is more effective in fresh oil and its effectiveness is reduced as the hours add up.

Researchers address long-standing mysteries behind anti-wear motor oil additive

The pistons in your car engine rub up against their cylinder walls thousands of times a minute; without lubrication in the form of motor oil, they and other parts of the engine would quickly wear away, causing engine failure. Motor oil contains chemical additives that extend how long engines can...

phys.org

 

[bullwinkle]

ZDDP is known to protect rings and cylinders in some cases. How much protection it offers and whether that protection applies to, for example, Nikasil coated bores with chrome or moly faced rings is unknown to me.

Adequate HTHS for hydrodynamic lubrication and ZDDP for protection of sliding parts such as cams, lifters, rings and cylinder liners.

Despite the claims that we have a replacement additive for ZDDP, we really don't. Test after test show it's effectiveness. It's also interesting to note that some tests show ZDDP is more effective in fresh oil and its effectiveness is reduced as the hours add up.

Researchers address long-standing mysteries behind anti-wear motor oil additive

The pistons in your car engine rub up against their cylinder walls thousands of times a minute; without lubrication in the form of motor oil, they and other parts of the engine would quickly wear away, causing engine failure. Motor oil contains chemical additives that extend how long engines can...

phys.org

Interesting-I've always heard the opposite-the detergents in fresh oil break down the tribofilm, which then requires heat & friction to reestablish itself again. As viscosity (& related hydrodynamic lubrication) continue to be lowered in pursuit of better economy, the tribofilm is often all that's left to prevent severe damage.

 

[Silver]

Interesting-I've always heard the opposite-the detergents in fresh oil break down the tribofilm, which then requires heat & friction to reestablish itself again. As viscosity (& related hydrodynamic lubrication) continue to be lowered in pursuit of better economy, the tribofilm is often all that's left to prevent severe damage.

This would insinuate a partial oil change may be ideal.

Edit: but if the detergents washed off the tribofilm ANYWAY, I guess you'd just be left with relatively depleted oil.

 

[kschachn]

The OP’s other thread has some really good links showing how ZDDP degrades over time. A partial oil change only contributes to the problem.

 

[RDY4WAR]

ZDDP is only active in boundary lubrication and is more effective on ferrous metals where the sulfur part of ZDDP reacts with iron surfaces to form a barrier of iron sulfide. The rod and main bearings operate in hydrodynamic lubrication and ideally should never encounter boundary lubrication. The rings go through all 3 lubrication regimes and rely on ZDDP at and near TDC and BDC up to ~20* each way.

There's no anti-wear additive that can replace ZDDP in effectiveness. However, there are other additives that synergize well with ZDDP, boosting anti-wear properties.

As with most anything, more ZDDP is not always better. ZDDP is created through reacting phosphorus pentasulfide with various alcohols to make dialkyl-dithio-phosphoric acid which is then neutralized (to a degree) with zinc oxide to form zinc-dialkyl-dithio-phosphate (ZDDP). This means ZDDP is an acidic ester. (neutral and basic ZDDPs exist but aren't used in engine oils) In some cases, too much ZDDP can cause corrosive wear. As far as interaction with detergents, ZDDP is acidic and detergents are acid neutralizers. You can see how that interaction can be conflicting. The synergy of ZDDP with other anti-wear / friction modifier / extreme pressure additives is also important and has to be accounted for when blending as more of one could throw off synergy with another and actually hurt more than help. This is why proper synergy of additives is important and why playing backyard shadetree chemist with a supplement is never a good idea.

 

[OVERKILL]

ZDDP is only active in boundary lubrication and is more effective on ferrous metals where the sulfur part of ZDDP reacts with iron surfaces to form a barrier of iron sulfide. The rod and main bearings operate in hydrodynamic lubrication and ideally should never encounter boundary lubrication. The rings go through all 3 lubrication regimes and rely on ZDDP at and near TDC and BDC up to ~20* each way.

There's no anti-wear additive that can replace ZDDP in effectiveness. However, there are other additives that synergize well with ZDDP, boosting anti-wear properties.

As with most anything, more ZDDP is not always better. ZDDP is created through reacting phosphorus pentasulfide with various alcohols to make dialkyl-dithio-phosphoric acid which is then neutralized (to a degree) with zinc oxide to form zinc-dialkyl-dithio-phosphate (ZDDP). This means ZDDP is an acidic ester. (neutral and basic ZDDPs exist but aren't used in engine oils) In some cases, too much ZDDP can cause corrosive wear. As far as interaction with detergents, ZDDP is acidic and detergents are acid neutralizers. You can see how that interaction can be conflicting. The synergy of ZDDP with other anti-wear / friction modifier / extreme pressure additives is also important and has to be accounted for when blending as more of one could throw off synergy with another and actually hurt more than help. This is why proper synergy of additives is important and why playing backyard shadetree chemist with a supplement is never a good idea.

One of the best explanations I've read about these synergistic relationships and how ZDDP functions on here, bravo! Extremely well explained!

 

[compratio10_5]

I don't think that your question can be answered simply. (Thanks Cuget for the paper on stress activated ZDDP tribofilms) Various parts of an engine operate in different lubrication conditions as reflected on the Striebeck Curve. The camshaft and valve actuation mechanisms are the most highly stressed contacts in an engine and operate in the boundary lubrication regime and must be protected from excessive wear by the ZDDP tribofilms since the oil films are too thin. Most engine bearings that have complete rotation operate with hydrodynamic lubrication (after start-up) and wear protection is provided primarily by the oil film thickness. The piston rings apparently operate with hydrodynamic lubrication in mid-stroke and boundary lubrication at the ends of the stroke so wear tends to be higher at the top end of the ring travel. According to the stress activated ZDDP theory, tribofilms develop more quickly and thicker in the more highly stressed contact areas so the thickness probably varies depending on location up and down the cylinder. ZDDP is a multi-functional additive so it also protects the oil from oxidation and protects the metal surfaces from corrosion and as such is a necessary component of modern engine oil.

 

[MolaKule]

...is the protecting film on cylinder walls is as thick as on the camshafts??...

Good questions and RDY4WAR has given a good set of explanations.

In the combustion chamber you have three things working against a thick hydrodynamic oil film:
1. thinning due to fuel dilution,
2. thinning due to heat, (Viscosity index)
3. turbulence due to aerodynamic swirls and chaotic flame patterns.

As RDY4WAR explained, when hydrodynamic lubrication starts to fail, then an anti-wear agent such as ZDDP comes to the rescue to provide a glassy film of protection.

Stribeck Curve - About Tribology

www.tribonet.org

There are some very good alternatives to ZDDP but as of now they are too expensive to incorporate in engine lubricant formulations in the same treatment levels as ZDDP, but are often used in some racing and boutique oils as secondary anti-wear agents.

 

[SR5]

Great thread everyone, thanks.

Just to add to it, here is an interesting article about ZDDP by Penrite, giving an interesting historical angle.

Knowledge Centre | Penrite Oil

ZDDP (Dialkyl Dithiophosphate), is a chemical compound used in engine oil as a sacrificial and very effective anti-wear agent. There has been a big focus on zinc, also known as ZDDP or ZDTP (zinc dithiophosphate). For many years this has been the anti-wear additive of choice for many engine oils...

penriteoil.com.au

"ZDDP was developed in the 1940’s initially as a bearing corrosion inhibitor before being used as a sacrificial anti wear agent for engine oils. From the early 1920’s to the mid 1980’s petrol contained tetraethyl lead which contributed to the build up of lead & lead oxides in the engine. Lead scavengers were then introduced but these caused acidic by products in the crankcase that reduced the effectiveness of the ZDDP. To counteract this, higher ZDDP dosages were introduced often into the range of 0.14 - 0.16%. The increase also pushed up levels of Phosphorus which is part of the ZDDP compound along with zinc.

......

There are many and varying opinions on what levels of Zinc are needed to be an effective anti-wearing agent in engine oils. Owners of vehicles that have flat tappet camshafts, veteran & vintage owners and traditionalists may argue that the higher the level the better especially in vehicles that do not have catalysts. This is not always the case. As we saw above, ZDDP was increased in oils to combat the effects of lead scavengers not actually to increase the anti-wear protection.

In effect, an engine oil that contains about 1000ppm or 0.1% phosphorus (approx.1100-1200 or 0.11-0.12% PPM Zinc) or higher, will easily provide the required anti wear properties for older engines. General Motors experimented in the mid 1950’s with lower phosphorus and zinc levels and found that 800PPM or 0.08% percent phosphorus level (approx. 1000 PPM or 0.1% Zinc) eliminated many wear issues. In fact, they also experimented with oils containing 600PPM or 0.6% phosphorus on mixed fleets in the 1970’s and found no wear problems."

 

[RDMgr]

What a fantastic and complex topic and only speaking to the reaction and not the application.

The paper discusses pressure at the asperity driving the reaction between the additive and the surface. This is essentially the root cause of the reaction. Pressure between surfaces creates heat which cause dissociation of the additive making primarily sulfur and/or phosphorus available for the surface reaction as READT4WAR indicates. Many years ago, I looked at the dissociation temperatures of antimony and other EP compounds with and without a catalyst (iron) by TGA. It helped give direction of additive selection in my area of interest which was enclosed gears, large open gears and high horsepower diesel engines utilized in mining machinery.

The reaction of sulfur and the iron (steel) of the surface creates a molecules thick layer of FeS that is intrinsic to the surface. This layer is more malleable that the original surface enabling the asperities to smooth. This is called the Rebinder Effect which is the reduction in the hardness and ductility of a material by a surface-active molecular film.

Other materials may be present in the contact region. These include oxides and medium to high molecular weight crosslinked or polymerized materials. These are likely not intrinsic to the surface.

Again, what a fantastic subject. It’s the crux of the work I did for more than 45 years.

 

[OilUzer]

Someone told me
ZDDP+Moly=Happy Engine

 

[4WD]

Lubricant Additives - A Practical Guide

A practical overview of oil and lubricant additives without all the chemistry.

www.machinerylubrication.com

 

[alcyon]

Great thread everyone, thanks.

Just to add to it, here is an interesting article about ZDDP by Penrite, giving an interesting historical angle.

Knowledge Centre | Penrite Oil

ZDDP (Dialkyl Dithiophosphate), is a chemical compound used in engine oil as a sacrificial and very effective anti-wear agent. There has been a big focus on zinc, also known as ZDDP or ZDTP (zinc dithiophosphate). For many years this has been the anti-wear additive of choice for many engine oils...

penriteoil.com.au

"ZDDP was developed in the 1940’s initially as a bearing corrosion inhibitor before being used as a sacrificial anti wear agent for engine oils. From the early 1920’s to the mid 1980’s petrol contained tetraethyl lead which contributed to the build up of lead & lead oxides in the engine. Lead scavengers were then introduced but these caused acidic by products in the crankcase that reduced the effectiveness of the ZDDP. To counteract this, higher ZDDP dosages were introduced often into the range of 0.14 - 0.16%. The increase also pushed up levels of Phosphorus which is part of the ZDDP compound along with zinc.

......

There are many and varying opinions on what levels of Zinc are needed to be an effective anti-wearing agent in engine oils. Owners of vehicles that have flat tappet camshafts, veteran & vintage owners and traditionalists may argue that the higher the level the better especially in vehicles that do not have catalysts. This is not always the case. As we saw above, ZDDP was increased in oils to combat the effects of lead scavengers not actually to increase the anti-wear protection.

In effect, an engine oil that contains about 1000ppm or 0.1% phosphorus (approx.1100-1200 or 0.11-0.12% PPM Zinc) or higher, will easily provide the required anti wear properties for older engines. General Motors experimented in the mid 1950’s with lower phosphorus and zinc levels and found that 800PPM or 0.08% percent phosphorus level (approx. 1000 PPM or 0.1% Zinc) eliminated many wear issues. In fact, they also experimented with oils containing 600PPM or 0.6% phosphorus on mixed fleets in the 1970’s and found no wear problems."

Modern Shell Helix Ultra 5W-40 has 1000ppm of zinc and 800ppm of Phos. I guess I am lucky I can this oil cheap.

 

[Johnmpb]

Wow, great thread. This is what bitog is all about. Bravo

 

[Cujet]

Interesting-I've always heard the opposite-the detergents in fresh oil break down the tribofilm, which then requires heat & friction to reestablish itself again. As viscosity (& related hydrodynamic lubrication) continue to be lowered in pursuit of better economy, the tribofilm is often all that's left to prevent severe damage.

Me too. In fact there are some who try to say that old oil protects better due to decreasing "per mile" wear metals. That's just not so when actual wear measurements are made. I worked for Mobil Oil as a tech in their flight department many years ago. We did some pretty serious oil and grease testing (Mobil 254 and SHC100 products) and measuring actual wear with scanning electron microscopes. I did chat with the engineers regularly. Even then, UOA results were just a tool, and DID NOT REFLECT actual wear rates. This serves to highlight the limitations of UOA results. Test after test show that dirty used oil increases the actual wear rate. If it were not the case, why change the oil at all. Contamination and particulates are a big reason, that's for sure. Additive effectiveness is another.

 

[qais90]

I appreciate your passion and Great knowledge in the above answers, thank you very much.

 

[OilUzer]

Regarding old oil & tribofilm, what I recall is not that old oil is good and protects better ... Rather some or a little left-over old oil helps ...

As a result, some were recommending changing the oil filter every other time. This would preserve some old oil (helps rebuilding or protecting tribofilm?) plus more effective filtering (filter age) as long as filter is not too old ... as new filters need some mileage to break in and be as effective ...

e.g. If doing 5K oci, change the filter every 10K miles. You'll then have some old oil plus a filter that doesn't spent an hour around the water cooler every morning ...

anyways, I'm not an oil expert and just using the above excuse to change my oil filter every other time with my older cars. I have short OCIs also so this won't cause any issues even if the above information is not %100 correct.

 

[930.engineering]

I'd suggest you re-read Cujet's post.