After 70+ years, the EPA mandated that all domestic oil producers remove ZDDP (Zinc Dialkyl Dithio Phosphate) from all conventional and synthetic motor oil. If your engine was designed before 1989 the non-roller lifters require ZDDP to avoid premature deterioration. ZDDP also alters bearing and journal surface characteristics to prevent metal to metal contact. Under extreme conditions like a high performance motor, ZDDP reduces the tendency of parts to scuff or gall under heavy loads. Simply add ZDDP-Plus to every 4-5 quart oil change and your motor will be protected from metal to metal contact. Add one 4 ounce bottle to a 4-5 quart oil change modifier to eliminate and metal-to-metal contact .

"ZDDPlus" is the best insurance to protect your classic or high-performance flat-tappet engine!" says NHRA's #1 Drag Racer of all time, "Big Daddy" Don Garlits.