Plenty of equity-based energy exchange traded funds have notched impress performances in recent weeks, but few have been durable all of this year.

The PowerShares Dynamic Energy Exploration & Production Portfolio (NYSEArca: PXE) and the PowerShares DWA Energy Momentum Portfolio (NYSEArca: PXI) have been exceptions, gaining 9.9% and 12.4%, respectively, year-to-date compared to 3.5% for the Energy Select Sector SPDR (NYSEArca: XLE).

The two PowerShares ETFs have benefited from their exposure to refiners.Refiners can prove durable when oil prices decline because those falling prices boost refining margins.

“Moreover, refiners often benefit from the fact that prices for refined oil products don’t drop as rapidly as crude prices, which means they can make extra profits until the so-called ‘crack spread’ eventually normalizes,” reports Clayton Browne for ValueWalk.

There is no dedicated refiners ETF on the market, but PXE and PXI serve as adequate proxies. The $183.2 million PXI tracks the DWA Energy Technical Leaders Index, which attempts to identify energy sector constituents displaying positive relative strength characteristics. With refiners among the energy sector’s relative strength leaders at the moment, PXI features robust refiner exposure. [Contrarian ETF Ideas for 2015]

Five of the ETF’s top 10 holdings are dedicated refiners. That quintet, which includes Tesoro (NYSE: TSO), Valero (NYSE: VLO)and Phillips 66 (NYSE: PSX), combines for 17.2% of the ETF’s weight. Several other of PXI’s 39 holdings, including Dow components Exxon Mobil (NYSE: XOM) and Chevron (NYSE: CVX), have downstream and retail operations as well.