[Fot] Zinc Additive.

[Enquiries Road & Track]

i have been using quite ordinary oils in my race 2500/TR6 engines for
almost 30 years and never had an oil related failure, eg cam lobes worn off

in recent years i have used off-shelf Mobil 1 (not the racing version). The
current version is called 15-50. See this table to check out its zinc &
phosphorous levels.
http://www.mobiloil.com/USA-English/MotorOil/Files/Mobil_1_Product_Guide.pdf

In my engine machine shop business we have seen this occur with flat tappet
V8 engines, especially old Ford side-valve ones and more recently Chevs,
but usually owners have filled them with very modern oils.

The "tappet" problem that people refer to is not restricted to old engines.
nearly every modern engine has a tappet (now days called a cam bucket), but
most modern OHC engines have very soft cam profiles and very large diameter
tappets. none-the-less, the oil shear problems can still occur .

.Terry