In the mid 1960s Chevron U.S.A was the first to market and produce a complete range of 100% synthetic Polyalphaolefins based lubricants, which began to be marketed as a substitute for mineral oils for engine lubrication. Although in use in the aerospace industry for some years prior, synthetic oil first became commercially available in an American Petroleum Institute (API)-approved formula for automobile engines when standards were formalized for synthetic-based lubricants.
Other early synthetic motor oils marketed included "The Original Syn!" by SynLube in 1969, NEO Oil Company (formally EON) in 1970, which were dibasic acide esters, or diesters, and polyol esters-based synthetic lubricants. In 1971 All-Proof, now called Red Line, introduced a synthetic oil, followed fourth by Amsoil who packaged and resold a diester-based 10W40 grade from Hatco[8] in 1972, and then Mobil 1, introduced in North America in 1974 (with a PAO-based 5W20 grade).
Source: Wikipedia