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, Sun Oil launched Sunoco ULTRA 94, the market's highest octane unleaded gasoline. Then in 1988, Sun undertook a 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 next door that Sunoco acquired from Chevron.