The average price of a gallon of gasoline in the U.S. has dropped 15 cents over the past two weeks, according to the Lundberg Survey of fuel prices, released Sunday, which puts the price of a gallon of regular at $3.48.

Midgrade costs an average of $3.65 a gallon, and premium is at $3.77. Diesel dropped 13 cents to $3.78 a gallon.

Jackson, Miss., has the nation’s lowest average price for gas at $3.03. San Francisco has the highest at $3.95.