If you project vehicle is pre-1989, ZDDP Oil Additive is a must for keeping that engine running smoothly If your engine was designed before 1989, the camshaft's non-roller lifters require ZDDP in the motor oil to prevent premature deterioration. However, the U.S. government recommended that ZDDP no longer be put into domestic motor oils starting in 1989, so today's motor oils won't provide the ZDDP your older engine needs...unless you add this ZDDP Oil Additive!

• ZDDP alters bearing and journal surface characteristics to prevent metal-on-metal contact
• ZDDP reduces the tendency of parts to scuff or gall under heavy loads
• Add a 4-oz. bottle of ZDDP to every 4- or 5-quart oil change