The "zinc" mentioned is zinc dialkyl dithiophosphate or ZDDP for short.
It aids lubrication in sliding/rubbing contact applications like cam/lifter contact.
Obviously the harder this contact the more important is the lubrication layer or oil film, so it is pretty minimal in our older engines at low rpm and light spring pressures--compared with heavy spring loading and max rpm for performance.
Cam grinders once included with the cam or recommended the use of EOS (engine oil supplicant)for their cam breakin--dip the lifters and anoint the cam during assembly then dump the rest in the crankcase.
EOS was marketed by GM and contained a heavy dose of zddp and ????--came in a pint can and was later changed to a quart can.
I don't think GM supplies anymore but WallyWorld and FLAPS will have a ADVERTIZED equivilent on the shelf.
Most premium motors oils once contained zddp before the heavy restrictions to protect cat converters etc limited it.
A WAY to easily identify the more desirable oils with zddp is to look closely at the nickel-sized circular product spec label on the container.at the top of the circle will be the oil design ratings like SF-SE-CC-CE etc. but what we are looking for is in the bottom part of the circle.if you find "energy conserving" the zddp has been left out--if the lower half is blank ZDDP is present.
Max zddp will be found in diesel engine oils(perfectly acceptable maybe even preferred ),racing oils, small engine oils, and motorcycle oils.
Our old engines are not terribly sensitive in my opinion.
Last edited by enginenut; 05/28/2012 12:55 PM.
