Crude supplies grew by 800,000 barrels, or 0.2 percent, to 372.6 million barrels, which is 11.5 percent above year-ago levels, the Energy Department's Energy Information Administration said in its weekly report.
Analysts expected a drop of 2.5 million barrels for the week ended Dec. 7, according to Platts, the energy information arm of McGraw-Hill Cos.
Gasoline supplies rose by 5 million barrels, or 2.4 percent, to 217.1 million barrels. That's 0.8 percent lower than year-ago levels. Analysts expected gasoline supplies to grow by 2.5 million barrels.
Demand for gasoline over the four weeks ended Dec. 7 was 1.3 percent lower than a year earlier, averaging 8.5 million barrels a day.
U.S. refineries ran at 90.4 percent of total capacity on average, down 1.2 percentage points from the prior week. Analysts expected capacity to increase to 91.8 percent.
Supplies of distillate fuel, which include diesel and heating oil, increased by 3 million barrels to 118.1 million barrels. Analysts expected distillate stocks to rise by 1.25 million barrels.
Benchmark crude rose 56 cents to $86.35 a barrel in New York.