The average price of diesel fuel in the United States fell again last week, dropping to levels last seen in mid-May, according to the latest numbers from the Energy Department.

The price of a gallon of on-highway diesel fuel fell 3.2 cents from the previous week’s price, settling at $2.316. Compared to the same week in 2015, the price is 30.1 cents cheaper.

Diesel prices were down in all regions of the U.S. with the largest decrease occurring in the Gulf Coast region, falling by 4 cents. The smallest change in prices was in the New England region where diesel fell by 1.8 cents.

The average price of regular gasoline was mostly flat last week, dropping only 0.9-cents to $2.15 per gallon. The price is 47.9 cents cheaper than it was a year ago.

Prices fluctuated depending on the region with the largest decrease occurring in New England with a drop of 4.3 cents per gallon. Prices were actually up in the Midwest where there was a 4-cent increase.

Crude oil prices have been falling in the past few months but were up around as of Aug. 8 due to renewed speculation that oil production may decrease to offset the lack of demand, according to MarketWatch.

Member countries of OPEC like Venezuela and Kuwait have indicated recently that they would like to reduce production to offset the lower global demand that has plagued the oil market since 2015. However, earlier this year OPEC countries failed to come to an agreement after similar speculation.