(personally I run Lucas Plus 20W50 , in the race engine. Very pleased with the performance per post season engine tear down) Also , Lucas, Amsoil , and I'm sure others sell kits where you can have a sample of your oil examined for wear indication. #1 owner of the Z happens to be an Amsoil rep.
Another online post:
I recently contacted the technical department of Lucas oil and inquired about the ZDDP content of the Lucas motor oils.
Here is what I was told
Standard 30W = 1265 parts per million
Standard 20W50 = 1265 parts per million
Standard 10W30 = 900 parts per million (has the seal oil industry seal and cannot exceed 900)
Racing synthetic 10W30 = 3031 parts per million
Racing synthetic 10W40 = 3031 parts per million
Racing synthetic 20W50 = 3031 parts per million
Here is a link to this oil http://www.lucasoiloffroad.com/lucas...SAE_10W-30.pdf
I have been using 10W30 Kohler Universal Engine oil in my Jeep to protect the Flat Tappet cam as the Kohler oil has around 3200 parts per million ZDDP but I think I will switch to the Lucas Synthetic Racing Oil at my next change now that I know that it has so much ZDDP in it and due to the availability of the Lucas products. The person I spoke with at Lucas assured me that the Lucas Racing Oil would hold up for my normal oil change interval of about 5000 to 6000 miles. Actually even the standard Lucas oil at 1265 parts per million would be more than enough to protect a Jeep 4.0 flat tappet cam.