U.S. gasoline inventories rose more than expected last week as refinery utilization improved, the Department of Energy (DoE) reported Wednesday.

In the week ending May 11, the nation's gasoline stocks increased by 1.7 million barrels, exceeding the 900,000 barrel gain expected by analysts, to 195.2 million.

That marked the second consecutive weekly gain in gasoline supplies. But the inventories were still well below the lower end of average for this time of year.

Gasoline supplies are closely watched as the summer driving peak is around the corner. Even though gasoline prices may be higher this summer, U.S. motor fuel demand will remain strong, the department predicted on May 8.

The increase in gasoline supplies came as the nation's refinery utilization was improving.

The DoE said refinery utilization rose a half percent last week to 89.5 percent, but still lower than the average of 91 percent to 92 percent for this time of year. As a result, gasoline production rose to an average of 9.1 million barrels per day.

U.S. commercial crude oil supplies, meanwhile, rose by 1 million barrels last week to 342.2 million barrels. The gain doubled the 500,000 barrel increase expected by analysts.

Stockpiles of distillates, which include heating oil and diesel fuel, also edged up 1 million barrels to 119.8 million last week. But the gain was less than the average analyst estimate of 1.2 million barrels.

The figures for commercial crude oil inventories do not include the U.S. Strategic Petroleum Reserve, which currently holds crude oil of about 689 million barrels.