The average price of regular-grade gasoline in the U.S. has remained relatively steady for the past three weeks with a national average of $3.01 per gallon.

Industry analyst Trilby Lundberg of the Lundberg Survey said Sunday that a drop in crude prices has not been seen at the pump. Lundberg says that station operators kept the difference between wholesale and retail prices to make up for tight margins.

The average on May 18 was a fraction under $3 a gallon.

The highest average price in the contiguous 48 states was $3.81 in the San Francisco Bay Area. The lowest was $2.54 in Baton Rouge, Louisiana.

The average price for diesel fuel rose 4 cents, to $3.27.

(AP)