WASHINGTON — A steep fall in gas costs pushed down a measure of U.S. consumer prices last month, keeping inflation mild.

The seasonally adjusted consumer price index dropped 0.3 percent in November from October, the Labor Department said Friday. Gas prices fell 7.4 percent, the steepest drop in nearly four years. That offset a 0.2 percent rise in food prices.

In the past year, consumer prices have risen 1.8 percent, down from October’s 12-month increase of 2.2 percent.

Excluding volatile food and gas, prices ticked up 0.1 percent in November and have risen 1.9 percent in the past year. Higher rents, airline fares and new cars pushed up core prices. The cost of clothing and used cars fell.