Exxon is one of the largest oil and gas companies in the world, and it has several competitors. CITGO, AMOCO, HESS, and ARCO are all five-letter and four-letter competitors of Exxon, respectively. CITGO is a subsidiary of the Venezuelan state-owned oil company PDVSA, while AMOCO is a former oil and gas company that was acquired by BP in 1998. HESS is an American integrated energy company, and ARCO is a brand of gasoline and convenience stores owned by BP.