USX <X> UNIT TO RAISE MOST CRUDE POSTINGS USX's subsidiary, Marathon Petroleum Co, said it will raise its contract prices for eleven grades of crude oil 50 cts a barrel, effective tomorrow. The increase brings Marathon's posted price for West Texas Intermediate and West Texas Sour grades to 17.50 dlrs a barrel. The Light Louisiana grade was also raised 50 cts to 17.85 dlrs a barrel.