Zinc Content
- Thread starter dybeepvw
- Start date
Patman
Staff member
For starters if you look in the VOA section here you can see the zinc levels in many different oils.
Here is Mobil1's list; Mobil1 Product Guide
Other manufacturers info isn't as easy to find, so you may have to email or use VOA's as noted.
Other manufacturers info isn't as easy to find, so you may have to email or use VOA's as noted.
OVERKILL
$100 Site Donor 2021
You are interested in the phosphorous content, that's what's limited by the API on xW-30 grades and below and the anti-wear part of the ZDDP compound.
Which engine and cam are you running? I have 2 flat tappet cam engines, both original to the car. If I ever pull them apart again, I will stab a hydraulic roller and be done with it.
Good luck.
As stated above, pay attention to the phosphorus content. Zinc dialkyl-dithio-phosphate (ZDDP) is the anti-wear additive in question when someone mentions "zinc" for engine oil. People colloquially shorten it to just the first part "zinc" though this has caused some confusion. It's actually a family of additives with nearly 200 different variants of ZDDP, not all created equal and with a rather wide range of reactivity and function. It's comprised of the elements zinc, phosphorus, and sulfur with various branching and chaining of various alkyl groups that dictate how the additive acts. The phosphorus and sulfur are the anti-wear elements, breaking down in boundary lubrication regimes to form barriers of ferrous disulfide and polyphosphate "glass" which help minimize metal to metal contact when insufficient oil film is present.
To break it down further, ZDDP starts out as phosphorus pentasulfide (P2S5). It's reacted with various alcohols (depending on which type of ZDDP you're making) to make dialkyl-dithio-phosphoric acid. This is the core of your anti-wear additive, but it's too acidic and unstable for use in this form. Thus, it is reacted further with zinc oxide to form zinc dialkyl-dithio-phosphate (ZDDP). Think of the "zinc" as a carrier for the molecule, keeping it stable long enough to get where it needs to go and do its job. Also, since ZDDP is created through a process of reacting acids with alcohols, ZDDP is a synthetic ester.
It's also the phosphorus and sulfur that's responsible for damaging emissions systems (though this is a overhyped issue) thus API limits phosphorus content in S-series oils to 800 ppm (with a minimum of 600 ppm) and sulfur content to 0.5% (0.6% for 10W-30, no limit on non-ILSAC grades of 40 and above). Oils that are not under API have no limit.
Also, there's more to play than just ZDDP content. A fully formulated oil is much more than just a single additive. Since you have a lot of different chemistry coming together to make the final product, that chemistry can oppose or synergize with one another. For example, ZDDP is an acidic ester and detergents are acid neutralizers. You can see how they may not like each other. On the other hand, ZDDP and MoDTC (moly-based friction reducing additive) compliment each other quite well, boosting the effectiveness of one another. Yet, there's other additives that can prevent that synergy. It's a careful balancing act, and simply dumping more ZDDP in an oil doesn't mean you'll get the full potential of wear protection that level could provide due to conflict with other additives. This is why I never recommend playing shadetree backyard chemist with supplements. There's a correct oil for every application, and if you have an oddball application, there are companies like HPL that will make one-off formulas to fit your application.
To break it down further, ZDDP starts out as phosphorus pentasulfide (P2S5). It's reacted with various alcohols (depending on which type of ZDDP you're making) to make dialkyl-dithio-phosphoric acid. This is the core of your anti-wear additive, but it's too acidic and unstable for use in this form. Thus, it is reacted further with zinc oxide to form zinc dialkyl-dithio-phosphate (ZDDP). Think of the "zinc" as a carrier for the molecule, keeping it stable long enough to get where it needs to go and do its job. Also, since ZDDP is created through a process of reacting acids with alcohols, ZDDP is a synthetic ester.
It's also the phosphorus and sulfur that's responsible for damaging emissions systems (though this is a overhyped issue) thus API limits phosphorus content in S-series oils to 800 ppm (with a minimum of 600 ppm) and sulfur content to 0.5% (0.6% for 10W-30, no limit on non-ILSAC grades of 40 and above). Oils that are not under API have no limit.
Also, there's more to play than just ZDDP content. A fully formulated oil is much more than just a single additive. Since you have a lot of different chemistry coming together to make the final product, that chemistry can oppose or synergize with one another. For example, ZDDP is an acidic ester and detergents are acid neutralizers. You can see how they may not like each other. On the other hand, ZDDP and MoDTC (moly-based friction reducing additive) compliment each other quite well, boosting the effectiveness of one another. Yet, there's other additives that can prevent that synergy. It's a careful balancing act, and simply dumping more ZDDP in an oil doesn't mean you'll get the full potential of wear protection that level could provide due to conflict with other additives. This is why I never recommend playing shadetree backyard chemist with supplements. There's a correct oil for every application, and if you have an oddball application, there are companies like HPL that will make one-off formulas to fit your application.
OVERKILL
$100 Site Donor 2021
Excellent explanation, I know you've made a similar effort in the past, always appreciated.
OVERKILL
$100 Site Donor 2021
OK, those are all roller motors, so they don't need crazy amounts of phosphorous.
Seriously, chemistry matters. LSjr has a great story he shared on Lubrication Explained about running a camshaft wear test using a known “bad” off the shelf reference oil and it doing far better than expected because in the move from SN -> SN+/SP the detergent package changed which boosted the ZDDP effectiveness.
Speaking of Zinc and Lubrication Explained, he put out a video the other week about the history of ZDDP
First of all tellus why you want to know and what vehicle is concerned...
Pardon my ignorance, what do you mean by “roller motors”?
In that case, Zinc is a non issue, end of story.
OVERKILL
$100 Site Donor 2021
Anything with a roller valvetrain, be it roller lifters or followers.
Older cars had flat tappets that rode metal-to-metal on the camshaft. Engine oils had higher levels of "Zinc" that acted as a sacrificial layer between components. If you ran higher than stock valve spring pressure, an elevated percentage of the additive helped to protect the cam lobe.
When catalytic converters came into play, and engines used roller valve trains, Zinc was lowered to about 700 to 800 ppm I believe.
In my 2 classics I use something like Castrol GTX. The engines are original to the cars.
Flat tappets with low/stock valve spring pressures should not be concerned.
Ex. Jeep 199/232/258/4.0L/2.5L Never had an issue with cams or lifters with SM - up limits. (2004)
I do run a more robust level in my bracket racer, however. Valve open pressures are nearly twice that of my Jeeps.
Ex. Jeep 199/232/258/4.0L/2.5L Never had an issue with cams or lifters with SM - up limits. (2004)
I do run a more robust level in my bracket racer, however. Valve open pressures are nearly twice that of my Jeeps.
OVERKILL
$100 Site Donor 2021
The API started restricting phosphorous back in the 90's for grades below xW-40. It was 1,200ppm under SH, then 1,000ppm with SJ in '96 (carried over to SL) and then with SM the limit was reduced to 800ppm, which is where it sits currently and why many Euro xW-30's stayed API SL, due to having higher levels of phosphorous.
The reason the limit is applied to lighter grades (RC ILSAC grades) and not the heavier one I believe is due to volatility and the more "pedestrian" orientation of the applications. Heavier oils are apt to be less volatile and ending up in the exhaust system, while lighter grades are more likely to be consumed/burned, potentially poisoning the catalyst. Heavier oils were generally also not spec'd for non-performance oriented applications.
Prior to the restrictions, phosphorous levels were all over the map, depending on the blender. We still see a bit of that with considerable variation in phosphorous levels below the 800ppm limit.
Unrestricted applications (eg, the Euro 0W-40/5W-40 oils) seem to keep phosphorous around 900-1,000ppm, so that appears to be the sweet spot with an unconstrained additive package, as if higher levels were beneficial, they would be used.
Roller valvetrains started to appear in common applications in the 1980's and catalysts even before that. Ford went roller in its passenger car applications in around 1985 with the 302 getting roller lifters. Truck applications continued to be flat tappet for whatever reason, up until sometime in the early to mid 90's (they also didn't get SEFI in '86 like the cars did). It wasn't until more than a decade later that real restrictions began to be imposed on phosphorous.
Of course aside from pushrod applications, sliding followers continued to be used by many European and Japanese marques. Cam-over-bucket is still common, with the lobe acting directly on the bucket situated on top of the valve. Honda was notorious for using solid valvetrains with sliding followers that required periodic adjustment.
Ultimately, AW chemistry is more complex than just a single compound, as @RDY4WAR has noted. There are synergistic and antagonistic relationships between different elements which can improve or diminish the AW performance of a given ZDDP compound. A poorly formulated "Classic Car" oil with 1,400ppm of phosphorous may be a markedly poorer performer than a heavily tested top-shelf Euro lube with 1,000ppm in actual AW testing.
However, the plebeian idea that "zinc" was removed (not just reduced) and that this will murder flat tappet applications has become legend. This mythos has permeated classic car culture and the market responded by spawned countless "classic car" oils of varying qualities with the focus being on pushing the presence of elevated levels of ZDDP and absolutely no manufacturer approvals. It's effectively a more innocuous version of the Lucas "Oil Stabilizer" fable, with Joe Average fully sold on the idea that there's this deficiency as result of the nefarious actions of "Big Oil" or the EPA but brother Lucas has your back with his magic elixir, which will "solve" this problem. Slapping "Classic" on some cheap API SH-era Group I/II swill with a bit more ZDDP as a top treat is a great marketing exercise along similar lines, but at least is a fully formulated product that's unlikely to cause any problems.
Ultimately, most flat tappet applications didn't have, and don't have, high enough spring pressures to require elevated levels of ZDDP. A 305, 350, 302 or 351W with a broomstick cam and long broken in lifters is arguably no more demanding (and likely considerably less so) than a more recent high winding cam-over-bucket or sliding follower application. Those that do would mostly be well served by just using an xW-40 full-SAPS Euro lube. Another option is to consider an oil that's on Ford's approved HDEO list, which all have higher levels of phosphorous per Ford's requirements and actually has passed OE testing and obtained approvals.
Well said.
I think the reason Ford went to roller lifters in cars was a compounding effect from wanting to improve fuel economy without sacrificing power or longevity. Moving away from carburetors to EFI was the prime ticket for accomplishing this, but so were changes in the valvetrain. Roller lifters can tolerate more aggressive ramps with a more rounded lobe which allows them to shorten the duration without sacrificing overall flow area under the curve. They could build more cylinder pressure, increasing torque (especially down low) and improving fuel economy.
There's some stock flat tappet engines that do still need more ZDDP in stock form, particularly Ford and Chevy big blocks due to the heavy valvetrain, high rocker ratio, big valves, and small lifter diameter. In an OHV (central cam) V engine with rockers, the rocker arm multiplies the force applied across it. The highest load is seen on the exhaust side when attempting to open the exhaust valve. This is because the valvetrain has to overcome residual combustion pressure in the cylinder to open the exhaust valve.
Let's take a stock 454ci BBC with oval port "290" heads which have 2.06" / 1.72" valves. Calculating exhaust valve surface area...
(1.72" / 2)^2 x π = 2.32 in^2 valve surface area
Cylinder pressure, with a stock engine and cam, is typically ~120 psi at the time the exhaust valve opens. This is multiplied by the valve surface area to get the load seen by the valve.
2.32 in^2 x 120 psi = 278 lbs
So there's 278 lbs seen by the valve against the residual cylinder pressure. The valvetrain must overcome this in order to open the valve, but it must also overcome the spring seat pressure which is ~90 lbs.
278 lbs + 90 lbs = 368 lbs
Since the rocker arm acts a lever, the load on the valve side is multiplied across the rocker ratio to the lifter side. The stock rocker arms for a BBC have a ratio of 1.7:1. Thus...
368 lbs x 1.7 = 626 lbs
This is the load seen by the pushrod and lifter the moment the lifter starts to climb the lobe. Inertia adds more on top of this. BBC has 0.842" diameter lifters which isn't a lot of contact area with the lobe so the force at that interface is immense. Also remember that the flat tappet lifters in these engines are constantly rotating. The lobe has an angle to it that spins the lifter. If the lifter stops spinning, it will dig into the lobe, destroying both the cam and the lifter. ZDDP provides enough cushion to keep that from happening.
By comparison, a 302ci SBF with larger diameter lifters (0.874"), smaller exhaust valves (1.60"), and lower rocker ratio (1.6:1) sees 530 lbs at the lifter. A 350ci SBC with yet smaller exhaust valves (1.50") and lower rocker ratio (1.5:1) sees 454 lbs.
For something like a Honda 4 cylinder OHC engine with the direct lobe to tappet setup, there's no rocker ratio to multiply the load and a lot less inertia thus the load seen at the lobe is significantly less. This is especially true of 4v pentroof heads where you have 2 smaller exhaust valves reducing the load to respective lobes. Thus, 600-800 ppm is perfectly fine even with radical cams. You'll never exceed what even a stock SBC or SBF sees. It's the same with flat tappet cams in small engines.
