The national average for the price of diesel fuel continued its downward trend by 1.3 cents to $3.975 for the week of March 31. Diesel, which remained above the $4-per-gallon level for the for four weeks ending March 17, is now 1.8 cents lower than the same period one year ago, according to the U.S. Energy Information Administration (EIA).

There are regions and states where diesel remains over the $4-per-gallon mark, including the East Coast ($4.09), New England ($4.25), Central Atlantic ($4.24), and California ($4.06), though even these high-price regions have seen prices fall over the last several weeks.

The price of gasoline, however, has increased in nine consecutive weeks since early February, but remains lower than the same week a year ago, when it cost 6.6 cents more, according to the EIA.

Gasoline rose in eight of the 10 regions tracked. The sharpest hike came in the Lower Atlantic region where it rose 5.9 cents. The Central Atlantic and Rocky Mountain regions fell slightly. Gasoline now costs at least $3.50 per gallon in 29 states.