Diesel fell for a third straight week, declining 1.3 cents to $3.975 per gallon, the Department of Energy reported March 31.
Average U.S. diesel prices have now decreased a combined 4.6 cents in the three weeks since March 10, when the national average stood at $4.021.
Diesel is 1.8 cents below its price in the corresponding week last year.
Gasoline, on the other hand, climbed 3 cents to $3.579 a gallon in the eighth consecutive weekly increase for the fuel.
Each week, DOE surveys about 400 diesel filling stations and 800 gasoline stations to compile national average prices.