Zinc additives for flat tappet lifter break-in

Zinc additives have been recommended by most engine manufactures for years.

So, why lower zinc and phosphorus levels in modern oils.

The American Petroleum Institute (API) has regulated the amount of zinc levels to .08 percent.

Consequently, due to its harmful effects on catalytic converters and emissions systems.

The latest API formulations are aimed at extending the life of catalytic converters.

Around 1996 most of the OEMs had already started manufacturing OHC engines with roller followers. That allowed them to use lower zinc-phosphorous anti-wear additives.

Today, the use of API approved oils in performance applications will likely lead to trouble. This is during flat tappet cam break-in periods.

All this has left a path of devastation and a lot of pointing fingers.

No Zinc Additives
No Zinc Additives

This has left the average hot rodders confused and uncertain as to the best course of action.

Various parties have blamed some of the failures on:

  • Camshaft manufacturing quality control
  • Inferior flat-tappet lifters
  • The aggressiveness of today’s modern cam profiles
  • Engine oil formulation

Most  of the serious complaints cropped up around the time that major changes occurred in both the flat-tappet manufacturing industry and in the formulation of passenger car and light-duty truck motor oils.

Many older engines experience a short period of time during engine start-up where critical lubrication is insufficient between metal-to-metal lubrication points when using modern oils with reduced amounts of ZDDP/ZDTP.

Most engine and engine component manufacturers recommend Zinc additives for flat tappet lifter break-in.

Many will void warranties if this minimum is not found in the oil sample you supply when returning broken parts for warranty. For this reason, many manufacturers produce their own zinc additives or oils with supplementary zinc included; GM offers its own EOS break-in oil with additional ZDDP.

Experts say that the additives in API blends will no longer cut it in a racing or performance engine. There is no denying that API oils for the most part work very well in late model engines where there are roller cams and much less friction than in high powered racing engines

“ZDDP is the predominant anti-wear additive used in crankcase oils. It is a class of additive rather than one particular chemical.

No Zinc Additives
No Zinc Additives

Not all Zinc (ZDDP) additives react under the same level of heat and load. Zinc has different “Burn” rates. Some Zinc additives have slower “burn” rates that require more heat and more load to activate than other Zinc additives.

Passenger Car Motor Oils typically feature a faster burning Zinc than Diesel Engine Oils due to the lower compression ratios found in gasoline engines compared to compression ignition diesel engines. As a result, not all “High Zinc” oils have the same activation rate.

Detergent additives “compete” against Zinc in the engine. Detergents are additives that clean the engine. Furthermore, detergents don’t distinguish between sludge, varnish and Zinc – it cleans all three away. The “old school” theory on engine break-in was to run non-detergent oils, and this allowed for greater activation of the Zinc additive in the oil.

Characteristics of Zinc and Detergents determine how quickly and to what extent an oil will provide sacrificial boundary film protection for your engine.

So after all this confusion what do you do !!

On late model engine with roller tappets use the factory recommended oil. Always keep up to dated with your maintenance.

On flat tappet camshafts.

There is a long list of great racing oils and additives out there and they are not all the same. I would think if your are looking for a great racing oil you must have a lot of friends and colleges out there doing the same thing.

Ask the guy beside you as they have most likely gone through it. I hate to say it but its cheaper to learn from someone else’s mistakes.

Every oil producer out there will tell you that theirs if the best, but seeing is believing and not all applications require the same oil.

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