Is Zinc Additive Really Needed For Older Engines?

“The past,” said English novelist L.P. Hartley in his 1953 novel The Go-Between, “is a foreign country; they do things differently there.” As far as book openings go, it’s pretty solid. Right up there with, “The sky over the port was the color of television tuned to a dead channel” or “The Man in Black fled across the desert, and The Gunslinger followed” in the pantheon of all-timer opening sentences. It’s also a pretty fair assessment of early to mid-20th century automotive technologies. From Babbitt bearings and drum brakes to carburetors and leaded gasoline, the old ways often seem strange and foreign to today’s car nerds. 

One very important automotive technology that’s changed dramatically over the years — although you might not think about it as “technology” the same as you would braking or suspension or engine management systems — is motor oil. In the past, motor oil had, as Derek Bieri likes to say, “All the vitamins and minerals old engines need.” Over the years, however, engines and emissions standards changed and motor oils changed with them. Nowadays, motor oils — both synthetic and organic, as it were — are optimized for use in brand new engines stuffed with bleeding edge technologies and tolerances measured in Plancks. 

What about older engines, though? What about our beloved Buick Nailheads and Chevy Small Blocks and Chrysler 440s? Do modern oils have enough of those good old vitamins and minerals to run safely in the engines that powered our fathers’ Oldsmobiles? 

Honestly? Yeah, for the most part. Modern oils, especially synthetics, are way better at keeping your engine safe and running at peak performance than the dinosaur squeezins your granddad used. The one area where today’s engine oils might be considered lacking is when it comes to the amount of zinc in the oil, and even then, it’s kind of an edge case that really only matters if you have a flat tappet cam.

See, back in the day, most engines had flat tappets to operate their valves and soft, cast-iron camshafts to go with them. Despite the fact that both flat tappets and roller tappets (and their attendant camshafts) had been around forever, the latter was the go-to for mass produced vehicles. That’s because flat tappet cams were cheaper, easier to produce, and tended to last the life of the car — remember, cars didn’t last as long in the old days. Only high-po one-offs and race cars had fancy pants roller cams. In the ’80s, though, as technology advanced, economy standards tightened, and horsepower demands increased, roller tappet cams became more common.

If you have an older vehicle with an engine that has a flat tappet cam in it, you should be using a zinc additive. How old, you ask? Well, if you’re rocking a V6 or V8 made before the mid-1980s, you’re probably going to want to throw some zinc additive into your crankcase every oil change. In the pre-roller tappet cam days, motor oils had more zinc in them. Zinc is slippery, and forms a very thin, sacrificial barrier between soft internal engine parts. The soft, cast iron camshafts used with flat tappets needed this sacrificial layer of zinc to prevent excess wear. 

With the rise of both roller tappets and catalytic converters, however, zinc became less of a thing in oils because roller tappet cams are made of harder materials and zinc has a bad habit of clogging up cats if it gets into the engine’s combustion chambers. That’s kind of a TL;DR explanation of the technical aspects of it, but you get the idea.

You can pick up Zinc additives just about anywhere auto parts are sold, and it’s not that expensive. If you’re not doing your own oil changes (why aren’t you doing your own oil changes?), your mechanic should definitely be able to get some zinc additive for you. Look at it like insurance — would you prefer to spend your money on a $15 bottle of zinc additive every few thousand miles, or an expensive, time-consuming, and possibly engine-out top end rebuild after you flatspot your cam doing burnouts?