Why a High Zinc Oil?
CARZ LLC
1212 East C Street
Casper, WY 82601

Office 307-266-0023
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Flat tappet cams are under a lot of pressure and require an extra oil additive for wear. New oils no longer have the additives we need for the extra protection required in the tight tolerances of race engines and flat tappet cam-shafted motors. The Zinc reacts with the metal to prevent wearing. More zinc will not better protect it will just protect for longer where metal to metal contact is high. The main concern with the old style motor oil is clogging of the catalytic converters on emissions controlled cars, so running a high zinc oil in flat tappet motors and race engines is recommended when no catalytic converters are used.
The question is do you want to use a synthetic oil or not. Synthetic oils have higher zinc levels, along with other preferred aspects, but will cost more than non-synthetics. There is a list of products with % of Zinc, .11 is good for normal use, ranging from just better that new conventional oil to just a step below race oil. Every oils Technical Data Sheet will give you the information you need. Some of the choices I have ran across include the following:
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What does the "W" in motor oil names stand for?
Answer at the bottom of this page.
It might surprise you...
The "W" stands for Winter NOT Weight
Castrol GTX-  API SG/CD Good for Gas and Diesel Engines natural or turbo .12% Zinc
Rotella T- API CJ-4 Better for flat tappet cams within OEM specs-NO Cats .13% Zinc
Valvoline All Fleet Good for Gas and Diesel Engines natural or turbo-NO Cats .15% Zinc
Spectro Golden Semi-Syn Good for higher HP applications, natural or turbo, and flat tappet cam-NO Cats .15% Zinc
Kendell GT-1 API SM/SL Good for higher HP applications, natural or turbo, and flat tappet cam-NO Cats .16% Zinc
Valvoline VR-1 Good for higher HP applications, natural or turbo, and flat tappet cam-NO Cats .20% Zinc

The prices determine what you want most of the time, but there are better oils in every price bracket. Out of the list above you can stay in the conventional to semi-synthetic oils and still cover stock to mild to hot cam set-ups. I would however recommend a full synthetic oil over conventional anytime due to the better overall protection package.