For years oil refiners have been riding the gravy train thanks to a large gap in domestic and foreign crude prices. For some refiners, this quarter was no different, but HollyFrontier (NYSE:HFC) didn't quite live up to expectations. Some of the disappointment has to do with the company's operations, but the narrowing of the price gap between foreign and domestic crude could be a troubling sign for refiners.

Some refiners will be able to weather the storm better than others, but there are some trends that investors can watch that should give them a picture of oil refiners' health in the future. In this video, contributor Tyler Crowe looks at some of the refiners that could continue going strong and what signs of trouble investors should look out for.