CAMARILLO, Calif. (AP) — The average U.S. price of a gallon of gasoline has dropped 21 cents over the past two weeks.

That’s according to the Lundberg Survey of fuel prices, released Sunday, which puts the price of a gallon of regular at $3.55.

Midgrade costs an average of $3.72 a gallon, and premium is $3.85.

Diesel dipped 7 cents to $4.08 a gallon.

Of the cities surveyed in the lower 48 states, Memphis, Tenn., has the nation’s lowest average price for gas at $3.11. San Francisco has the highest at $4.05.

In California, the lowest average price was $3.81 in Sacramento. The average statewide for a gallon of regular was $3.98.

(Copyright 2012 The Associated Press.)