Rust Defense System protects engines from moisture contamination caused by running through streams and bogs or frequent short-trip service. Superior anti-wear technology reduces valve-train wear, and piston and ring scuffing. Superior deposit control – controls sludge and varnish formations for cleaner and cooler running engines. Performs equally well in air-cooled and liquid-cooled engines. Low volatility base oils minimize oil consumption. Replacement for Polaris’ PS-4 (SAE 5W-50).