The EPA has started a new campaign to eliminate our old vehicles - they have removed all the Zinc and most of the Phosphorus from todays motor oil to protect the catalytic convertors in the newest vehicles. But, zinc and phosphorus in older pre 1996 motors lublicates flat tappet cams to prevent wear, and protects the older bearings in these same motors from excessive wear. Now that SM grade motor oil does not have these elements, they must be added in at every oil change to prevent damage to cams and bearings. The additive is ZDDP and it is available from many sources - all cars from the mid 90's and older need this additive. Comp Cams and Edelbrock are now marketing oils and additives to address this for muscle cars and other older vehicles. If you want to keep driving your trucks or other older vehicles, using this additive is imperative to longevity of the motor. I am just so glad the EPA is looking out for the auto makers to help them save money on replacng damaged convertors due to Zn and Ph contamination - just like the ethanol is leaning out carb equipped motors so they burn up. This does apply to all our trucks motors as they all were designed for the Zn and Ph to be in the oil.