WASHINGTON — A steep fall in gas costs pushed down a measure of US 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 biggest 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 the volatile food and gas categories, prices ticked up 0.1 percent in November. Core prices have risen 1.9 percent in the past year — below the Federal Reserve’s annual target of 2 percent.

Higher rents, airline fares, and prices of new cars pushed up core prices last month. The cost of clothing and used cars fell.

‘‘In simplest terms, inflation is not a problem,’’ said Jim Baird, chief investment strategist at Plante Moran Financial Advisors.