Zinc, Engine oil and flat cams

[SirRobyn0]

So a little over a year ago I had a thread going regarding this very topic. A few opinions were thrown around a long with what oil folks have used and had good luck with. At the shop at the time we were using a ZDDP additive when we had a classic car owner ask for high zinc oil, since then I've researched and learned a heck of a lot about ZDDP and what it does and doesn't do. To that end we still only use high zinc oil by request but have switched to using Valvoline VR1. So I'm going to try to summarize what I've learned in hopes that it will help anyone that isn't sure if they should be running high zinc oil or regular oil.

For this article I'm sticking to just what I read or watched from interviews or articles written by oil scientists, regarding the need or possible need for high zinc oil in a flat tappet cam.

For the sake of this discussion it will be focused on conventional oil not synthetics, but the same principles apply to both.

ZDDP also commonly called zinc is Zinc dialkyldithiophosphate a complex chemical compound that in engine oil coats the inside of the engine, heat helps to essentially bake it on. Since camshafts are not lubricated well, and flat tappets cause the camshaft to contact and slide across the bottom of the lifter, lubrication is especially important. But just oil alone is not good enough, especially when under high stress, and at start up so zinc on the cam and lifters keeps the lifters from dishing and camshaft lobes from flattening out.

Facts: Zinc was introduced into engine oil in the 40's first at very low concentrations it was originally used to reduce corrosion. When engineers realized the cam wear benefits the concentrations quickly went up to about 500PPM, until 60's where it started going up again. Topping out in the 70's at an average of 1,400PPM. The problem with ZDDP is that when it burns off in the combustion process even in small quantities it coats the exhaust and reduces catalytic converter efficiency. So starting in the early 80's zinc levels have been on the decline. And in part do to the lower zinc levels oil now has more detergents in it. Allowing longer gaps between changes and cleaner engines.

The current API rating limits ZDDP levels to no more than 800PPM, and most all even discount oils are very close to that 800 limit.

Race oil or off road oil does not have to conform to API ratings so those oils can have more.

Diesel oil can have more ZDDP in it, but some formulations are low zinc. The higher zinc content diesel oils that I'm aware of are as follows:
Chevron Delo 15W40 1,100ppm
Mobile Delovac 15W40 1,050ppm
Shell Rotella 15W40 1,150ppm (seems to be gold standard of choice if using a diesel oil for flat tappets)
O'reilly's heavy duty oil 15W40 1,130PPM

But wait there is more. As a general rule the ZDDP levels in diesel oil have been going down as well. The down fall to Diesel oil is that it is very high detergent. Those high detergents will have the tendency to "wash away" a lot of that zinc before it has a chance to do it's job. That is one of the reasons that higher detergent oils didn't come along sooner for gas engines. Also the reason that oils such as VR1 and other high zinc oils have "reduced detergents and are not suitable for extended oil change intervals. We recommend no more than 3,000 miles between changes on VR1". That quote came from an Valvoline oil scientist. The scientist that would go on to say that if your running a stock engine with a well broken in camshaft that todays modern oil is likely to be just fine. If it's a high performance engine with heavier valve springs or high lift cam then VR1 would be the better choice. But again keep in mind that VR1 does not have as much detergents as modern oils.

A few high zinc oils and their levels:
Valvoline VR1 10W30 & 20W50 1,400PPM
Joe Gibbs Driven HR 1,400PPM

It is also possible to have to much zinc, to high of levels can cause damage. Generally speaking in a street engine it is unlikely you need anything over 1,400PPM. One of the reasons that zinc additives are not recommended, also it seems to be largely unknown how well those additives do or don't mix with whatever flavor of oil your using. At the very least if your going to use a zinc additive have a UOA done on the oil with the additive in it to be sure your not getting to high or not high enough.

Summary: If your running a well broken in engine regular modern oil is probably just fine, unless you push the engine a lot, example: A truck that tows or hauls heavy loads. If you do a lot of that or want a little added protection, then you might want to choose a diesel oil or a high zinc racing oil. If you choose to run a diesel oil, (make sure you pick one with higher zinc), your probably going to get some benefit from it, but the high detergents may work against the higher zinc levels to some degree. If your running a high lift cam and / or heavy valve springs it might be a good idea to choose a high zinc racing oil.

So there, not trying to tell anyone what to do, and if you have been using an oil and it's been working for you I'm not suggesting that you change it, but if your not sure what is best maybe this will help you out.

 

[SirRobyn0]

I didn't want to post this in the main post, but I'd like to add this. On my personal truck I've been running regular conventional Valvoline 10W30, plus substituting a 1/2 quart with hyper-lube stabilizer. The reason being is that I run the truck pretty hard from time to time either loaded heavy or with the trailer, I figured it could use the extra protection of the stickiness. I've had pretty good luck on other vehicles with hyper-lube reducing oil leaks and smoking so I felt comfortable using. I run it in my Jeep which has lifter noise on start up and with the hyper-lube it doesn't do that. however in my research I learned hyper-lube stabilizer and the Lucas version are essentially just a thick sticky base stock without many if any additives. Fine for what it is I guess, but if you pour it in your engine you are thinning the other additives out. So in my example the 800PPM zinc in my motor oil might be closer to 700PPM after I've subbed out some of the oil with hyper-lube. My engine is stock and I change the oil every 3K, but I've decided to try diesel oil. I picked up a 2.5 gallon jug of Rotella and change the oil this morning. I do get a little puff of blue at start up do to worn valve stem seals, the hyper-lube did not seem to help that much if at all, so I'll be curious to see if the diesel oil changes it at all. 200 mile feed run tomorrow so I'll let you all know if I notice anything.

 

[Rusty Nail]

I ran Rotella 15-40 in the IROC two oil changes after I bought it.
Then I felt it was slowing it down too much so I switched to conventional Valvoline 5w-30.
I'm glad I was able to guarantee introduction of those chemicals and the byproducts in that foreign to me crankcase prior to use.
Felt confident that the engine reached a place where it wasn't none too pleased and became lazy and sluggish but it took awhile..200 miles not sufficient but let it get in there real good..
Fun experiment for sure!

It's an old engine. Old conventional oil is okay. No zinc worries.
If the engine were new, new oil would be better and zinc would matter running pushrods.

 

[75gmck25]

I find it more convenient to buy locally, so I try to use oil I can find on the shelf at the parts store.

Mobil 1 15W50 is designed for flat tappet engines and it has 1200/1300 Phosphorous/Zinc. I used to find it on the shelves at Autozone, but usually not in the large 5 quart bottles. Mobil 1 0W40 is also 1000/1100.

I have now swapped to a retrofit roller cam, so I haven’t checked lately for high ZDDP products.

 

[Shorty81]

I use this in BBC

You must be registered for see images attach

 

[fussfeld]

Here are my thoughts. And i'm NOT saying high ZDDP levels are even needed with stock/stock cam valve springs? Who knows?

But to be safe, here's what i did:
(Note: All my RUNNING cars have roller lifters, so now i just use Mobil 1 synthetic. Yes, i've joined the 21st century. You should too......)

1) When i ran flat lifters, i liked to change the oil at 5000-7500 miles.

2) i used Redline synthetic---it has the high ZDDP content:
https://www.redlineoil.com/10w30-motor-oil

This worked out to be about $35-$40 MORE per oil change as compared to Mobil 1 or "regular" oil as i can get a 5 gallon jug of either mobil or other brands for $22 at walmart.

So, i figured the $40 more every 5-6 months or so was cheap insurance IF high ZDDP was even needed.

If i had used conventional oil then the price difference would be even less because synthetic can go longer than conventional between changes. (?)


Since it's not clear whether high ZDDP is needed to begin with, i feel $40 more per oil change is cheap insurance.

 

[fussfeld]

double post

 

[fussfeld]

i should add that they were stock-ish 305's and 350's. So, is higher ZDDP even needed with those engines?

Stock cams, stock valve spring pressures.....

 

[Rusty Nail]

Not in my professional opinion and not in my cars either.

 

[SirRobyn0]

i should add that they were stock-ish 305's and 350's. So, is higher ZDDP even needed with those engines?

Stock cams, stock valve spring pressures.....

Not in my professional opinion and not in my cars either.

As said in the initial post from a Valvoline oil scientist "if your running a stock engine with a well broken in camshaft that todays modern oil is likely to be just fine". For a stock engine, the one exception most of these guys had was for RVs, and trucks that do a lot of towing and hauling. It's hard to get these oil scientists to give yes / no answers and I think part of that is they don't want you to try to sue the company if your cam takes a crap. But it seems to me that diesel oil is preferred to racing oil for a stock engine that is run hard (towing, hauling, RVs ect). I think at least in part due to the reduced detergents in racing oil.

So @fussfeld I agree with @Rusty Nail No not needed in a stock engine, and keep in mind running high zinc has down falls to.

To add to that, I have always run regular conventional in my stock 305 in my square, my stock 445 in my Cadillac and when I had my 77 Class-c RV which was on a Dodge Chassis. I use to tow with that RV as well. I did run 20W50 in it, but just normal conventional. I did switch my square to diesel 15W40, but I do run that 305 pretty hard sometimes when loaded, maybe that's not the right word, but I'll run it at higher RPMs to keep it in the power band. Wanting to get away from the Hyper-lube made 15W40 look like a good choice and if I get a little added protection that's a bonus, and it's got plenty of detergents to keep it clean. Plus it's cheap.

My opinion for what it's worth I think the whole reduced zinc thing is blown out of proportion, but also I do think some modified engines do need higher zinc.

 

[Rusty Nail]

Dude you were doin good too!

But then what happened here?

My opinion for what it's worth I think the whole reduced zinc thing is blown out of proportion, but also I do think some modified engines do need higher zinc.

 

[SirRobyn0]

I find it more convenient to buy locally, so I try to use oil I can find on the shelf at the parts store.

Mobil 1 15W50 is designed for flat tappet engines and it has 1200/1300 Phosphorous/Zinc. I used to find it on the shelves at Autozone, but usually not in the large 5 quart bottles. Mobil 1 0W40 is also 1000/1100.

I have now swapped to a retrofit roller cam, so I haven’t checked lately for high ZDDP products.

The most recent OA report I can find on the internet is from 2019, and it appears the levels were the same at that time, however I will point out to anyone that doesn't realize this, both of these oils are synthetic.

I use this in BBC

I removed the picture in the quote to save space. Schaeffer's 10W30 Supreme 7000, is a full synthetic. Schaeffer's website indicates that it could have anywhere from 1700 - 2100PPM zinc. According to most of what I have read this is high enough to possibly be to high for some engines.

 

[SirRobyn0]

Dude you were doin good too!

But then what happened here?

Let me guess, because in my first post I said I was going to stick what the oil scientists are saying and then I gave my opinion. "my opinion for what it's worth".... Well yea, I know it's about worthless anyway lol.

 

[Daveo91Burb]

I've used Lucas Hot Rod and Classic Car oil in my '76 Vette (vortec heads on the original 350, but still flat tappet cam) for at least the last five years. No issues at all. Before that I was using Joe Gibbs, but it's a lot more expensive than the Lucas.

Hot Rod & Classic Car 10W-30 Motor Oil

Lucas Hot Rod & Classic Car Motor Oil SAE 10W-30 is manufactured with the highest quality paraffinic base oils and is fortified with a unique additive package containing high levels of zinc, molybdenum and phosphorus, which provides a tougher, thicker additive film for maximum protection even un...

lucasoil.com

 

[Raider L]

I have used a conventioal oil in my engine from the start, Pennsoil 10w30, and used that from the time way back in the '70's. My Brother -in-Law was rebuilding his W30 455 4-4-2 and was putting it together with Pennsoil. At that time I used Quaker State. That oil he was using was so slippery I couldn't believe it so the next time it came time to change oil I used the Pennsoil in my wifes Buick Century Special 231 V6. In two weeks you could look in the oil fill hole in the valve cover and see perfectly clean valve springs and every little casting dimple in the head surface. Before, you were lucky if you could see into the hole in the valve cover for all the sludge buildup from Quaker State. I kept wondering what was causing all that sludge. The oil wasn't removing it, the Pennsoil did. So I put it in my truck and sure enough it did the same to my truck. Now, I don't know how much zinc Pennsoil used to have in it but it sure did save engines. When we took my engine apart to rebuild it, it was perfectly clean inside, the oil pan to. Whatever was in the oil prevented wear and tear on the engine, even the crank was only worn down .002" on the journals.

Now I look for the API "S" whatevers the oil is supposed to have in it to be compatible for older engines, like "SL" "SU" and a couple of others I can't remember right now. I've read that API "SN" is for more modern engines, "SM" is another one. Anyway, that's what I look for to make sure it's like the older oils. Rotella is one of those oils that's good for older type engines with flat tappet cams because it has the other formulations with probably zinc in it.