This is really strange, something I found out recently and confirmed tonight. ChevronTexaco doesn't operate or supply Texaco stations. Shell bought the Texaco stations when Chevron bought the Texaco exploration and production business. The map for "branded motor fuels" at ChevronTexaco.com shows only Chevron stations in North America, and Chevron and Texaco stations coexisting under ChevronTexaco only within the great nation of Kazakhstan. ChevronTexaco kept the Texaco stations in Latin America, but sold those in North America to Shell. Actually, Shell and Texaco already had a joint marketing venture, which explained the cross use of Shell and Texaco cards. Shell simply bought the other half of the venture, which operates or supplies both Shell and Texaco stations.
