Oil refiners have lagged behind other energy stocks for most of the year, but they could turn around. While there are no refiner-focused exchange traded funds on the market, investors can still look at diversified energy funds with some exposure to familiar and obscure refining names

“After being on the sidelines for the bulk of this year, we feel the relative underperformance in the refining group provides an opportunity to start nibbling,” Howard Weil analysts Blake Fernandez and Richard Roberts said in a note, Barron’s reports. “Those feeling they had missed their opportunity to participate in the US energy renaissance may have another shot.”

Notably, Fernandez and Roberts upgraded Holly (NYSE: HFC) and Valero Energy (NYSE: VLO) to “Sector Outperform” from “Sector Peform” and made Marathon (NYSE: MPC) a “Focus Stock.”

ETF investors interested in taking on refiner exposure can consider the PowerShares Dynamic Energy Exploration & Production Portfolio (NYSEArca: PXE), which tracks U.S. companies involved in exploration and production of natural resources used to produce energy.

PXE has a 2.4% weight in HFC, 4.8% in VLO and 4.7% in MPC.

The PowerShares ETF surged 3.6% over the past week and increased 20.7% year-to-date.