Tesoro Corp. said Monday it is buying the Wilmington refinery and about 250 retail sites in Southern California from Shell Oil Products for $1.6 billion.

The refinery produces about 100,000 barrel per day of heavy, sour crude refined to meet California’s stringent air quality requirements. Included in the deal is about $200 million worth of inventory.

Based in San Antonio, Tesoro owns six refineries in Alaska, California, Hawaii, North Dakota, Utah and Washington, with a combined capacity of 563,000 barrels per day. Tesoro markets fuel to 478 branded gas stations, including more than 210 company-operated stations in the western United States

“These assets are a tremendous complement to our existing operations on the West Coast and will be immediately accretive to our earnings and cash flow,” said Tesoro Corp. Chief Executive Bruce Smith

Shell Oil Products is a unit of Royal Dutch Shell plc., the world’s No. 3 oil company. It is based in the Netherlands.