LONDON—Oil prices fell on Sept. 7 as a rise in stocks of refined petroleum products offset a sharp decline in U.S. crude inventories to the lowest level since 2015.

Brent crude futures were down 34 cents at $76.16 a barrel by 8:46 a.m. CDT. U.S. West Texas Intermediate (WTI) crude futures slipped 64 cents to $67.13 per barrel.

Both contracts were set for their first weekly loss in three weeks.

U.S. commercial crude oil inventories fell by 4.3 million barrels to 401.49 million barrels in the week to Aug. 31, the lowest since February 2015, U.S. Energy Information Administration (EIA) data showed on Sept. 6.

But sentiment suffered due to a rise in refined product stocks coupled with relatively weak demand for fuel during this summer’s U.S. driving season—when consumption normally peaks.

Gasoline stocks rose by 1.8 million barrels, while distillate stockpiles, which include diesel and heating oil, climbed by 3.1 million barrels, the EIA said.

“(Gasoline) stocks ... are now 3.5% above the year-ago level. More worryingly, the surplus to the five-year norm now stands at 5.4%, the highest since June 2017,” Stephen Brennock of London brokerage PVM said.

“This bears all the hallmarks of a disappointing summer driving season. As a result, the alarm bells are now ringing that a gasoline glut will persist for the foreseeable future,” he added.

On the supply side, U.S. crude oil production last week remained at a record 11 million barrels per day, a level it has largely been at since July.