Independent gasoline station owners filed an antitrust lawsuit accusing Texaco Inc., Shell Oil Co. and a Saudi oil company of conspiring to fix gasoline prices. The U.S. District Court lawsuit, filed in Los Angeles, claims the three companies have tried to use joint marketing ventures to fix prices since 1996 while raising rents and the wholesale prices dealers must pay for gasoline. The goal, the owners contend, is to replace small independents with bigger company-owned stations. Company representatives said the allegations were false. Creation of the ventures was the subject of a yearlong investigation by the Federal Trade Commission and attorneys general in several states where the companies operate. No wrongdoing was found, Texaco spokesman Andy Norman said.