Investors returned to the oil and gas pipeline industry's largest exchange-traded fund during July, despite relative stagnancy in stock and crude oil prices during that time.

The Alerian MLP ETF, which tracks the index, saw $83.8 million in net inflows in July after a net $15.5 million flowed out during June. The Alerian index dropped less than 1% in July on a total-return basis, which includes distribution income, after gaining 2.6% in June.

Master limited partnerships, which house billions of dollars of U.S. oil and gas pipeline assets, are not taxed at the corporate level but pay relatively high quarterly distributions to stockholders.

MLP share prices have remained stagnant, while midstream corporations are getting a hefty boost through their exposure to passive investment vehicles such as the S&P 500. Analysts at Wells Fargo said Enterprise Products Partners LP, Energy Transfer LP, Magellan Midstream Partners LP and Plains All American Pipeline LP could also be eligible for that index if they elect to become C-corporations, putting them in a position to reap similar benefits.

Still, the sentiment around investing in the energy industry at large remains lukewarm. A dozen broader energy ETFs tracked by S&P Global Market Intelligence saw nearly $354 million in combined net outflows in July as the price of West Texas Intermediate crude rose less than 1% to settle at $58.58 per barrel July 31.

"Even though it's been five years since oil cracked, it doesn't feel like the general mood towards fossil fuels or energy stocks is improving," CBRE Clarion Securities associate portfolio manager and MLP expert Hinds Howard wrote in a July 21 blog post. "It may be a while yet before our summer of discontent reaches the twilight or winter that would signal an end of energy under-performance is near."