The average U.S. price of a gallon of gasoline has dropped two cents over the past three weeks.

The Lundberg Survey of fuel prices released Sunday says the price of a gallon of regular is $3.64. Midgrade costs an average of $3.82 a gallon, and premium is $3.96.

Diesel was down three cents to $3.90 gallon.

Of the cities surveyed in the Lower 48 states, Jackson, Miss., has the nation's lowest average price for gas at $3.20. Chicago has the highest at $4.48.

In California, the lowest average price was $3.81 in Sacramento. The highest was in San Francisco at $3.97. The average statewide for a gallon of regular was $3.92, down 11 cents.