Statoil and four other service station operators in Sweden are under investigation for possible illegal price-fixing.
The Swedish competition authority has been looking into Norsk Hydro Olje, OK-Q8, Preem Petroleum, Svenska Shell and Statoil Detaljhandel since December.
This investigation was launched after the companies moved in November to cut down on discount schemes for corporate customers.
"We felt that these discounts were excessive, particularly in relation to the pump prices charged to ordinary consumers," says Johnny Ohlsson, head of Statoil Detaljhandel in Sweden.
"Eliminating them was intended to bring down the level of discounts and thereby maintain reduced pump prices in order to enhance our competitiveness in the market, rather than to boost profits."
The competition authority is checking whether the companies engaged in an illegal exchange of information during this period.
Statoil Detaljhandel's legal advisers are due to submit their comments to the authority in June. During the summer, the latter will then assess submissions from the five companies and reach a final conclusion.
"We welcome this investigation, since we take a very serious view for commercial and competitive reasons of breaches both of competition law and of our own internal policy," says Mr Ohlsson