Delek US Holdings, Inc.DK is a diversified downstream operator with interests in refining, wholesale distribution of refined products, and convenience retail. Click to get this free report Delek US Holdings, Inc. (DK): Free Stock Analysis Report HollyFrontier Corporation (HFC): Free Stock Analysis Report Par Pacific Holdings, Inc. (PARR): Free Stock Analysis Report To read this article on Zacks.com click here. Agreed, gasoline prices usually rise during this time of the year as motorists take to the roads for summer travel but it seems that the fuel is starting to go up too much.