Silver, engine parts containing

ZDDP (zinc dialkyl dithiophos-phate or zinc diaryl dithiophos-phate)—widely used as an anti-wear agent in motor oils to protect heavily loaded parts, particularly the valve train mechanisms (such as the camshaft and cam followers) from excessive wear. It is also used as an anti-wear agent in hydraulic fluids and certain other products. ZDDP is also an effective oxidation inhibitor. Oils containing ZDDP should not be used in engines that employ silver alloy bearings. All car manufacturers now recommend the use of dialkyl ZDDP in motor oils for passenger car service. 

Corrosion A lubricant base oil must not contain components which corrode metal parts of an engine or a machine. The problems of oxidation products leading to corrosion have been mentioned above and corrosion tests usually involve bringing the base oil sample into contact with a metal surface (copper and silver are often used) under controlled conditions. Discolouration of the metal, changes in surface condition or weight loss may be used to measure the corrosion tendency of the oil. 

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