2 Oil Refiners In Merger Deal For $1 Billion
Diamond Shamrock Inc and Ultramar Corp to merge through exchange of stock to form Ultramar Diamond Shamrock, independent oil refining and marketing giant; deal is valued at about $1 billion; Rodger R Hemminghaus, who will be chairman and chief executive, says firms expect to save about $75 million a year; Jean Gaulin will be vice chairman, president and chief operating officer (M)