Petrox was a detergent additive used from 1954 to 1989 by Texaco, in its premium-grade "Sky Chief" gasoline. A new plant in Port Arthur, Texas was built to manufacture Petrox. Petrox continued to be used in Texaco's highest-octane gasoline for more than 30 years even after its leaded "Sky Chief" grade was replaced in 1981 by "Super Lead-free Sky Chief", which was renamed "Texaco Super Unleaded" in 1982.
Due to Petrox lowering the octane of the fuel, it was replaced by "System 3" in 1989, which in turn was succeeded by "Clean System 3" fuels in 1994.
References
Petrox Wikipedia(Text) CC BY-SA