Retail investors curious about investing in oil have a couple of options—they can invest in oil companies that benefit from high oil prices or, if they'd like more direct exposure, they can trade oil futures. But futures trading can be complicated and risky for inexperienced investors, making an oil ETF a more accessible way to gain direct exposure to oil prices.

Oil prices, as measured by the Bloomberg Composite Crude Oil Subindex, have dropped by 26% over the past 12 months, significantly underperforming the S&P 500 Index’s 20% gain.

There are six distinct oil commodity ETFs that trade in the United States, excluding inverse and leveraged ETFs as well as funds with less than $50 million in assets under management (AUM).

Below we look at the oil ETFs with the best 12-month performance, lowest fees, and most liquidity. All numbers are as of Jun 16.

Oil ETF with the Best 1-Year Return: United States Brent Oil Fund LP (BNO)

• Performance Over One-Year: -25.8%
• Expense Ratio: 1%
• Annual Dividend Yield: N/A
• Three-Month Average Daily Volume: 691,100
• Assets Under Management: $184 million
• Inception Date: June 2, 2010
• Issuer: USCF Investments

BNO is structured so the daily percentage change in the spot price of Brent Crude oil is mirrored by the percentage change in BNO's net asset value (NAV). The fund's benchmark is the near-month futures contract unless that contract is within two weeks of expiration, in which case the benchmark is the next month's contract. BNO invests primarily in Brent Crude futures, but it may also invest in forwards and swap contracts.

Oil ETF with the Lowest Fees and Most Liquidity: United States Oil Fund LP (USO)

• Performance Over One-Year: -26.6%
• Expense Ratio: 0.6%
• Annual Dividend Yield: N/A
• 30-Day Average Daily Volume: 3,946,679
• Assets Under Management: $1.67 billion
• Inception Date: Apr. 10, 2006
• Issuer: USCF Investments

USO is structured as a commodity pool and is meant to mirror the percent change in the spot price of West Texas Intermediate, a light sweet crude oil delivered to Cushing, Oklahoma, that acts as a benchmark price for U.S. oil. The contract is traded on the New York Mercantile Exchange (NYMEX). USO invests in other oil-related contracts and may invest in forwards and swap contracts.

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As of the date this article was written, the author does not own any of the above ETFs.