A group of Unocal 76 service station owners, alleging a conspiracy to control the availability and price of oil and gasoline products, filed a federal antitrust suit seeking to block the sale of El Segundo-based Unocal Corp.'s retailing and refinery arm in Orange County. Unocal agreed last year to sell its 76 Products Co. subsidiary to Tosco Corp. for nearly $2 billion. The suit contends that Unocal should have offered the station operators the opportunity to buy their own stations. Station owners were notified in December that their property leases and contracts to purchase fuel from Unocal would be terminated early because of the Tosco deal. Station owners now will have to renegotiate their leases and contracts with Tosco. A Unocal spokesman said there is "absolutely no conspiracy." The station owners are seeking an order halting the transaction until a trial on the lawsuit. A hearing is scheduled Tuesday in U.S. District Court in Los Angeles.