Amoco

In 1930, Standard completed its acquisition of Sinclair Pipeline and also acquired the remaining half of Sinclair Crude Oil Purchasing Company. The two companies were renamed to Stanolind Pipeline Company and Stanolind Crude Oil Purchasing Company. The pipeline company headquarters were located in the Philcade building in Tulsa, Oklahoma. In 1950, all of the corporation's pipeline activities were merged into a single entity, which was named Service Pipeline Company. By 1964, the company operated 14,500 miles of pipelines located in the central part of the country. It gathered crude oil from 34,300 wells and carried it to 59 refineries, delivering 900,000 to 950,000 barrels a day.

Lead-free gasoline

While most oil companies were switching to leaded gasolines en masse during the mid-to-late 1920s, American Oil chose to continue marketing its premium-grade "Amoco-Gas" (later Amoco Super-Premium) as a lead-free gasoline by using aromatics rather than tetraethyllead to increase octane levels. This was decades before the environmental movement of the early 1970s that led to more stringent auto-emission controls, which ultimately mandated the universal phase out of leaded gasoline.

The "Amoco" lead-free gasoline was sold at American's stations in the eastern and southern U.S. alongside American Regular gasoline, which was a leaded fuel. By 1970, lead-free Amoco was introduced in the Indiana Standard marketing area in 1970. The Red Crown Regular and White Crown Premium (later Gold Crown Super Premium) gasolines marketed by parent company Standard Oil (Indiana) in its prime marketing area in the Midwest before 1961, also contained lead. By 1978, Amoco had phased out premium lead gas.

In November 1986, amid pressures from the EPA to cut down on the usage of lead in gasoline, Amoco became the first major oil company to say it would quit all retail sales of leaded gasoline. In its place, Amoco began selling a mid-grade 89 octane unleaded gasoline (the same number as its leaded regular gasoline), along with its unleaded regular and unleaded premium offerings.

World War II

World War II followed this period of exploration; Indiana Standard participated in the war effort, discovering new means of refinement and even a way of producing TNT more quickly and easily. In addition, Indiana Standard significantly contributed to the aviation and land gasoline needed for the Allied armies. Also, during the war Indiana Standard created its chemical division, formed from the merger of the Pan American Chemicals Company and the Indoil Chemical Company.

Post-war

In the late 1940s, after World War II, Indiana Standard returned to focusing on domestic oil refinement and advancement. In 1947, Indiana Standard was the first company to drill off-shore, in the Gulf of Mexico, and in 1948, Stanolind Oil invented Hydrafrac, a hydraulic well fracturing process that increased oil production worldwide. Initially the Hydrafrac process was licensed exclusively to Halliburton.

By the early 1950s, Standard Oil of Indiana was ranked as the second-largest American oil company with annual gross sales of $1.5 billion. It had 12 refineries in the United States, marketed its products in 41 states, owned 12,000 miles (19,000 km) of crude oil pipelines, 10,000 miles (16,000 km) of trunk lines, and 1,700 miles (2,700 km) of product pipelines.

In October 1954, Standard Indiana opened its Mandan refinery in North Dakota under its American Oil Company subsidiary.

Business expansion

In the late 1950s and early 1960s, Indiana Standard began to diversify its assets. It again led the way with scientific and technological discoveries. Indiana Standard discovered PTA, a chemical for polyester fiber production. In 1968, following that discovery, Indiana Standard acquired the Avisun Corporation and Patchogue-Plymouth, forming the Amoco Fabrics and Fibers Company. By 1992, the company was trying to sell off its yarn factories in Alabama and Georgia.

The company's Amoco Foam Products subsidiary made polystyrene cups, plates, carrying trays and other products. The division was sold to Tenneco in June 1996.

Amoco

In 1956, the Pan-Am stations in the southeastern U.S. were rebranded as Amoco stations. In 1961, Indiana Standard reorganized its marketing giving its American Oil Company unit responsibility for its retail operations nationwide under the Standard name inside the Indiana Standard marketing area (Colorado, Illinois, Indiana, Iowa, Kansas, Michigan, Minnesota, Missouri, Montana, Nebraska, North Dakota, Oklahoma, South Dakota, Wisconsin, and Wyoming) and under the American name outside that region. Both brands shared the same redesigned torch and oval logo for easy identification nationwide. The Utoco (Utah Oil Company) name used in Indiana Standard's southwestern region was replaced by the American name. The Amoco name continued to be used outside the U.S. and as a brand on certain American Oil products.

Soon after, the company began to expand. With an exploration office in Canada, Indiana Standard was now an international gas company. Indiana Standard created several new plants and claimed various new oil fields in this time period, as the company prospered in the post-war boom.

By 1971, all the divisions of Indiana Standard bore the Amoco name including American Oil which was renamed Amoco Oil with American stations renamed Amoco stations. By 1975, Amoco began phasing in the Amoco name in the old Indiana Standard sales territory. Standard Oil Company (Indiana) was officially renamed Amoco Corporation in 1985. Facilities, like the one in Casper, were renamed using the new branding.

Phillips Petroleum's assets in the General American Oil Company, acquired in 1983, were later taken over by Amoco.

Carlin's Amoco Station was built at Roanoke, Virginia, around 1947; it was listed on the National Register of Historic Places in 2012.

Global expansion

Standard of Indiana established operations in Venezuela during the 1920s under dictator Juan Vicente Gomez. However, by 1932, during the worst of the Great Depression, the company sold its interests to Standard Oil of New Jersey.

In 1958, Indiana again went overseas by signing a deal with Iran to develop oil interests in the Middle Eastern country, this marked the company's first expansion into the Middle East. However, during the 1978 Iranian Revolution, Indiana faced significant challenges as political unrest escalated. The company swiftly shut down its Iranian operations and evacuated all American employees after they received death threats. This marked Amoco's complete withdrawal from Iran.

In the following decades, Amoco expanded globally, creating plants, oil wells, or markets in over 30 countries, including Italy, Australia (acquired by BP in 1984), Britain, Belgium, Brazil, Argentina, South Korea, Taiwan, Pakistan, Norway, Venezuela, Russia, China, Trinidad and Tobago, Egypt, West Germany. In addition, the company also acquired a division of Tenneco Oil Company and Dome Petroleum Limited becoming one of the world's largest oil companies.

In April 1981, reorganized Amoco Production, Amoco Oil, Amoco Chemicals, and Amoco Minerals—its four main units—into worldwide operating concerns. The Amoco International Oil Company was also merged into Amoco Production, with its refining and marketing operations transferred to Amoco Oil and its marine transportation operations made part of Indiana Standard's supply and technology department.

In July 1988, Amoco acquired Dome Petroleum, a Canadian company. By 1989, Amoco was the fifth-largest gasoline seller in the United States with more than 14,000 stations in 30 states.

In 1994 Amoco was involved in a consortium with nine other companies that signed an agreement with the government of Azerbaijan for exclusive rights to develop oil fields in the Caspian Sea. Also in 1994 Amoco combined with competitors Shell Oil and Exxon to construct a $1 billion offshore oil platform in the Gulf of Mexico, the deepest in the world at the time.

Merger with BP

By the end of the 1990s, worldwide oil prices had slumped to their lowest point in over a decade. Amoco, the fourth largest US oil producer at the time, reported a 50% fall in earnings in second quarter of 1998. Analysts believed Amoco was hurt by its lack of international refining. On August 11, 1998, Amoco announced it would merge with BP in the world's largest industrial merger.

Though billed as a merger of equals, BP held control of the new entity. Shareholder control was split 60/40 in favor of BP shareholders. The new company was also based in London, where BP was based, with BP chief executive Sir John Browne running the company. BP chairman Peter Sutherland and Amoco chairman Larry Fuller served as co-chairs. The consolidated company would also cut 6,000 jobs worldwide.

The new company made efforts to further consolidate by announcing the acquisition of Atlantic Richfield Company (ARCO) for $26.8 billion in April 1999. However, it wasn't until BP Amoco agreed to divest ARCO's Alaska holdings that the FTC approved the deal a year later. The company then cut 2,000 jobs.

In August 1999, BP Amoco sold its western Canadian oil properties for $1.1 billion, to Canadian Natural Resources ($690 million) and Penn West Petroleum ($410 million). In September 2001, BP Amoco sold its refineries in Salt Lake City and Mandan, North Dakota to Tesoro Petroleum.

Originally, the plan was for all US BP service stations to be converted to Amoco while all overseas Amoco service stations were to be converted to BP. But by 2004, BP announced that all Amoco service stations would either be closed or renamed to BP service stations, including the remaining stations still bearing the "Standard" name. BP also chose to rename its gasolines with the Amoco name, changing its midgrade and premium offerings to the Silver and Ultimate brandings that Amoco used. By 2008, the "Amoco Fuels" name had been mostly discontinued in favor of "BP Gasoline with Invigorate". The Amoco name, however, lives on as BP continues to sell Silver and Ultimate under the BP name.

In addition, a few BP stations continued operation under the Amoco name. Most were either converted to BP, demolished and replaced with BP-style stations, abandoned, or switched to competitor brands. On April 1, 2010, in Mississippi, Chevron purchased some BP gas stations, which had been Amoco, to convert them to the Texaco brand.

In the aftermath of the Deepwater Horizon oil spill in the Gulf of Mexico, there were reports in the press that BP was reconsidering rebranding itself as Amoco in the US. Some independently owned BP stations, including former Amoco stations, switched to a different brand due to the public relations fallout as a result of the oil spill.

The Amoco brand returned to the Pittsburgh market in fall 2020, when locally based Coen Markets announced a marketing deal with BP to sell Amoco-branded gasoline at all of its fuel-offering locations. As most of Coen's stores were already selling BP gasoline (with a small handful having been Amoco stations before BP), this marked the largest switchover from BP to Amoco since the brand's reintroduction, though a few Coen stations were also selling Exxon, Sunoco, and Citgo prior to the deal. While the deal didn't affect BP as a whole, as BP lost several stations in the market to Marathon Petroleum years before, it essentially relegated the BP brand to 7-Eleven stations in the market as well as a few independent operators.

Following the acquisition of TravelCenters of America in May 2023, BP began converting all pumps to either BP or Amoco branding. In February 2024, there were 675 Amoco gas stations in the United States. In May 2025, Amoco has 900 stations across the United States.