The national average price of a gallon of diesel dropped nearly 4 cents this week to $3.894, falling for the third week in a row, according to weekly figures from the U.S. Department of Energy.

That's still 66.3 cents higher than it was a year ago.

The highest average price was in California, at $4.122, driving the average for the West Coast region as a whole to $4.061. The next highest region was New England at $4.036, while the lowest prices were seen in the Gulf Coast at $3.828.

Gasoline showed a smaller drop, falling 1.6 cents per gallon from last week to a $3.274 national average. That was the fourth week in a row for lower gas prices. The highest prices, as for diesel, were on the West Coast at $3.476, lowest in the Gulf Coast states at $3.087.

Oil prices fell $1.64 Monday to $97.77 a barrel on the New York Mercantile Exchange, the lowest in more than two weeks. The oil market is being affected by developments in Europe, with investors concerned that a recession in the region could cut into worldwide oil demand.