The Oil Price Information Service (OPIS) is the worldâ€™s most comprehensive source for petroleum pricing and news information. They maintain a database of U.S. wholesale petroleum prices, receiving more than 70,000 rack prices each day. The OPIS API lets users connect to a web service to query the site database. The Database is updated in real-time and the data can be integrated into a user's web site. Documentation is not publicly available.