The Stovebolt Site Forums The Shop Area Engine Shop Reformulated Engine Oil

Randy Baumann,

Lots has been written on this subject, and many folks opinions based on misunderstood info! Here is my unprofessional take on the topic.

You are probably referring to Zinc, which is a extreme pressure additive added to motor oil. I think it is shown as ZDDP in the list of ingredients, and the levels have been reduced to help auto makers achieve emission requirements.

This additive isn't critical in any engine you would find in a old Chevrolet car or truck. Most of these engines were produced when the oil of choice was non-detergent which had few anti-wear additives.

The lack of this zinc can be a factor in the cam lobe/lifter interface of a new engine with high performance (stiff) valve springs. This area can wear rapidly, transfer material and generally fail in very short order if a metal to metal situation is allowed. It's a smearing/shearing zone and requires something to keep it lubricated until the surfaces wear and polish to each other.

Some of the API diesel rated oils contained sufficient amounts of ZDDP to satisfy this cam/lifter problem area, but I understand even those oils are having their levels of zinc reduced.

There are aftermarket additives that will solve this problem.

These are hot-rod, big cam solid-lifter engines with big valve springs or dual valve springs. Most engines with flat tappet cams aren't effected. Most modern engines use roller cams so this critical boundary zone doesn't exist.

That's my take on this often hot topic.

Stuart