For the fourth week in a row, diesel prices fell in the U.S., this time by less than half a cent, according to the latest numbers from the Energy Department.

The average price of on-highway diesel fuel slipped by 0.4 cents last week, settling at $2.558 per gallon at the pump. Despite falling prices in the past month, diesel fuel is now 55 cents more expensive than it was in the same week of 2016.

Prices were down across the country, except on the West Coast where prices were up by 1.1 cents. The largest decrease in prices occurred in the Midwest, where a gallon of diesel fell 0.8 cents last week.

The average price of regular gasoline was nearly flat for the week, falling 0.3 cents per gallon at the pump to settle at $2.293. Regular gasoline is now more than 53 cents more expensive than it was in the same week last year on average.

Both the West Coast and Midwest actually saw slight price increases last week, rising 2.2 cents on the West Coast. The largest decrease in prices occurred in the Central Atlantic region, where prices fell 2.6 cents per gallon.

Rising crude-oil production in the U.S. caused prices to fall. That offset the efforts of oil-producing countries in the Middle East to freeze and reduce oil production output. Crude oil prices had been creeping up for the past week, but by the end of trading on Feb. 6, oil futures saw the largest single-day loss in several weeks, according to a MarketWatch report.