Investors are buying into the United States Oil Fund, lifting shares outstanding to a two-month high on speculation crude prices will rebound from the lowest level since August as refineries complete seasonal maintenance work.

The share count climbed to 194.6 million, up 18 percent from this month’s low of 165.3 million on Oct. 2, according to fund data compiled by Bloomberg. A net $379.4 million has been poured into the biggest oil-exchange traded fund this month, following a $392.8 million outflow last month.

The rise in shares outstanding comes as West Texas Intermediate crude has dropped nearly 5 percent this month to the lowest level since August amid rising U.S. inventories and lower refinery demand. Refineries typically boost their operations in November as they finish seasonal maintenance. Average crude use increased by 5.1 percent in the past four years from early November to early December.

“People are putting bets now, knowing that oil will probably go up when refineries boost their demand next month,” said Carl Larry, head of oil and gas for Frost & Sullivan LP in Houston.“As refineries continue to run higher, you’ll see prices get lifted more.”

Refineries conducting fall maintenance include Chevron Corp.’s Richmond, California, plant, Phillips 66’s Wood River, Illinois, refinery and CVR Refining’s Coffeyville, Kansas, refinery. Nationwide fluid catalytic cracker outages for the month of October average about 772,553 barrels a day, the highest average for the time period since at least 2011, according to data compiled by Bloomberg.

WTI futures dropped $1.12 to $42.86 a barrel on the New York Mercantile Exchange at 12:41 p.m. TUesday in New York after falling to $42.58, the lowest intraday level since Aug. 28. The U.S. Oil Fund, which holds WTI futures, slipped 32 cents to $13.69. The CBOE Crude Oil Volatility Index, which measures the volatility of the ETF, increased to 44.49.

Refinery oil input rose for the first time in one month in the week ended Oct. 16, up 0.4 percent to 15.6 million barrels a day. From 2010 to 2014, crude use averaged 15 million in early November. It increased to 15.8 in early December.

U.S. crude inventories increased to 476.6 million barrels in the week ending Oct. 16, the highest level since May.

“We are nearing the end of the maintenance season,” said James Williams, an economist at WTRG Economics, an energy- research firm in London, Arkansas. “We are going to see refineries coming up and that should start drawing crude supplies down.”