In Canada, Sunoco is operated by Suncor Energy, a separate Canadian entity. Sunoco is a Fortune 100 Company. It is also the biggest company based in Philadelphia and the 2nd biggest in Pennsylvania behind AmerisourceBergen.
With a growing portfolio of oil fields and refineries in hand, Sun opened its first service station in Ardmore, Pennsylvania in 1920. The name changed back to Sun Oil Company in 1922 and, in 1925, Sun became a publicly traded company on the New York Stock Exchange. Following World War II, Sun expanded internationally. Its first Canadian refinery was built in 1953 in Sarnia, Ontario, home to a burgeoning new petrochemical industry. Sun established a facility at Venezuela's Lake Maracaibo in 1957, which produced over a billion barrels (160,000,000 m³) before the operation was nationalized in 1975.
In 1968, Sun Oil merged with Tulsa, Okla.-based Sunray DX Oil Company, which refined and marketed gasoline under the DX brand in several midwestern states, and included several refineries including one in Tulsa that is still operated by Sun to the present day. This move expanded Sun's marketing area into the mid-continent region.
Sun Oil continued marketing its petroleum products under both the Sunoco and DX brands through the 1970s and into the 1980s. In the late 1980s, Sun began rebranding DX stations in the Midwest to the Sunoco brand and even introduced the high-octane Sunoco ULTRA 94 gasoline to stations in that region, but by the early 1990s, they pulled out virtually all areas in the southeastern US and west of the Mississippi, resulting in the closing and rebranding of service stations and jobbers to other brands in those areas, notably Sinclair in Oklahoma.
With increased diversification, Sun Oil Company was renamed Sun Company in 1976. In 1980, Sun acquired the U.S. oil and gas properties of Texas Pacific Oil Company, Inc., a subsidiary of The Seagram Company, Ltd., for US$2.3 billion -- the second largest acquisition in U.S. history to that date.
Through the 1980s, Sun developed oil interests in the North Sea and offshore China and expanded its holdings in both oil and coal with additional U.S. business acquisitions. In 1983, consumers saw the arrival of Sunoco ULTRA 94, the market's highest octane unleaded gasoline. Then in 1988, Sun undertook a major restructuring to segregate its domestic oil and gas exploration and production business and the focus the company on its refining and marketing business. This led to the acquisition of Atlantic Refining and Marketing (and, in effect, that company's convenience store chain, A-Plus), including its Philadelphia refinery which was later merged with the former Gulf Oil refinery right next door that Sunoco acquired from Chevron.
By the 1990s, Sun had departed the international exploration business and was fully dedicated to its branded products and services. Sun sold its remaining interest in Canada's Suncor Energy in 1995, but jointly operate two refineries in Toledo, Ohio, and Sarnia, Ontario, in joint ventures. The "Sunoco" became central to the company in 1998 when Sun Company, Inc. became Sunoco, Inc.
In 2003, the Speedway SuperAmerica chain of gas stations and convenience stores exited the southeast United States and sold most of their operations to Sunoco. Shortly prior to this, Sunoco acquired many service stations from Coastal Petroleum, especially its stations in Florida. This has led to the reintroduction of the Sunoco brand to areas it pulled out of several years earlier.
After ConocoPhillips abandoned the marketing of the Mobil brand name in the Washington, DC, area, Sunoco purchased these rights, and has since been converting Maryland and Virginia Mobil stations to the Sunoco brand, bringing the A-Plus convenience store with them (these stations before had convenience stores under the Circle K or On the Run brands). Most of the conversions done so far have been in Virginia.
Researchers at the University of Massachusetts Amherst have identified Sunoco as the 55th-largest corporate producer of air pollution in the United States, with roughly 1.7 million pounds of toxic chemicals released annually into the air. Major pollutants indicated by the study include nickel compounds, naphthalene, aniline, and benzene.