Hello Joel. Lead was removed from gasoline in the mid 70’s and gas filler caps began to display the unleaded fuel only warning.
This was purely environmental as lead was only put in to cheaply bring up the octane level of gasoline, the side effect was better valve train life.
Those of us that grew up at that time recall the tailpipes of cars being white inside after a long highway cruise, which was the lead as it exited the hot exhaust pipe.
Zinc was removed from oil in 1994, as it was shown to clog catalytic converters.
It was soon discovered that older flat tappet engines, (especially fresh rebuilds) needed the zinc to help cushion the camshaft from the lifters.
Engine shops suddenly were swamped with rebuilt engines prematurely wearing out the camshafts with the new oil.
Zinc additives were developed and oil manufacturers began to offer high zinc racing oils to resolve the problem.
Engines with roller lifters do not require high-zinc oils but non-catalyzed performance and older engines still benefit from Zinc.
Mark
Classic Car Restoration Club

Because of EPA demands to reduce the level
of anti-wear agents, (to protect catalytic converters), all gasoline oils must now (2023) be considered SMOG OILS that will
not protect flat-tappet engines.
The solution is diesel oils, although, the
EPA and the SAE oil-ratings folks are also
promoting reduced zinc/phosphorus levels
in diesel oils also, but not as badly as the
gasoline oils. Recent oil analysis tests indicate that Shell Rotella is OK, but Ford’s
Motorcraft diesel oil is better, as Ford has
declined to participate in the latest smoggy
SAE diesel-oil rating system, maintaining
a previous higher-level of anti-wear agents.
Bottom line: You want to use a diesel oil
that says “not for use in gasoline engines”,
because…those are the best oils for older
cars without catalytic converters.
The EPA doesn’t care about lubrication
problems in older flat-tappet engines.

Interesting response. I was a mechanic 50+ years ago and never heard of this Zinc issue up to your post. Every mechanic, restorer, etc that I know recommends 100% synthetic oil at the weights called for in the original manual for any/all cars made from the 50’s to today.

Hello Steve,

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Thanks!

However I’d disagree with adding Zink solutions to Oil. This was information was given to me decades ago when Zink was removed

However In a thread a few years ago there was a heated debate re adding Zink, which lead (no pun intended) to an embarrassing statement to a member who had emphatically wrote that all the ingredients in engine oils where blended carefully, at a heated temperature ,, etc.. was incorrect in a very Nasty statement.

His reply was that He was in Fact a Petroleum Engineer with decades of experience,, etc.. etc ..

I can add that I’ve had several friends that have had early Flat Lifers fail, common denominator being adding A Zinc additive themselves. One Very experience builder the Lifters failed on a Fresh engine build during the initial engine break in period. Oh, He’s also a Perfectionist

What Do the great company’s that make these secondary additives , They emphatically State their products are perfect , research , blah blah blah.

ME, I don’t take any chances, and when I owned Flat tap lifters I always purchased Engine Oil that Contained Zinc,, why take the chance

I only have one SBC but it’s a GM performance ZZ4 crate engine with a Roller Cam assembly. The other 4 are LS engines and I onot utilize Synthetic engine oil it’s just to Expensive and time consuming to take a chance

Can I blend a perfect mix of Zinc, will it be perfect ?? Possibly but I choose to be in the cautious side

I do recall much Rhetoric when, was it Corn based alcohol, was added and not much in the way of warning re old cars with Carbs etc,,, Most of use k is that and many leaned a nasty lesson when broke down in the road of often in the home garage after our Classic of Street Rod wouldn’t start.

Case in Point. Acid Rain …

Michael. EE / CE , never be short sighted and take the risk

Whatever you DO NOT put Rotella or any other synthetic oil in that car! It will damage any cork gaskets and other gasket material used back then. Unless you’re driving a lot of miles , you can forget about stainless valves and hardened seats. Also if you drive your classic like I drive mean (relatively minimal) you put a simple fix for the alcohol issue. Put in a fuel shut off near the carb so you can shut the fuel off run the carb (I can already hear the comments lol). But it works pretty good for low mileage driving and it’s quick and inexpensive to do.

Great little Ford ( and I’m a Chevy guy). Have fun and drive it!

Michael