Pennzoil's proprietary additive package, Z-7¨ is used in all Pennzoil single-grade and multigrade oils. A technologically advanced formula, Z-7 exceeds the U.S. and import car, truck, and van warranty requirements for all gasoline engines. Designed to prolong engine life, Z-7 contains:

Antiwear agents that react chemically with metal surfaces to produce a protective coating in high-load areas (such as cams, valve lifters, valve-stem tips, and rocker arms), where the oil film otherwise might break down.

Detergent-dispersants that pick up microscopic engine contaminants and hold them suspended so they can be removed with the oil when it is changed. They are added to the oil to prevent sludge and varnish formation.

Rust and corrosion inhibitors that neutralize the acids formed by condensation and contaminants, preventing rusting and corrosive wear on engine surfaces.

Oxidation inhibitors that prolong oil life by preventing oxidation, the chemical reaction of oxygen and oil that can thicken the oil excessively, form sludge and varnish, cause ring sticking, and corrode bearings.

Foam inhibitors that break down the foam produced when air is whipped into the oil by rapidly moving parts. Foaming can diminish the oil's lubricating and cooling capacity, promote oxidation, reduce oil pressure, produce air pockets, and even cause the oil to overflow the crankcase.

Friction modifiers that minimize friction between moving parts. These additives reduce engine power requirements and help improve fuel economy.

Viscosity modifiers that reduce the thinning of oil at high temperatures and the thickening of oil at low temperatures, allowing the oil to work more effectively through a wide range of temperatures.