Tesoro Corporation (NYSE: TSO) operates as an independent petroleum refiner and marketer in the United States.^[1] The Company's primary segments are divided into Refining and Retail, through which its manufactures and sells transportation fuels such as gasoline, jet fuel, diesel, and other petro-products.^[2] Its refining customers include wholesale and bulk marketers and its retail customers include mainly end-users of gasoline and diesel.^[3] As a petroleum refiner, Tesoro's revenues depend on the spread between its crude feedstocks and the price at which it can sell its refined products, which is known as the refining margin.^[4] Supply interruptions and lower demand due to economic slowdown have led to smaller spreads, which has impaired profitability.^[5]

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