The average U.S. price of a gallon of gasoline has dropped six 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 $3.78.

Midgrade costs an average of $3.94 a gallon, and premium is at $4.06.

Diesel dropped six cents to $4.09 a gallon.

Of the cities surveyed, Memphis has the nation’s lowest average price for gas at $3.34. San Francisco has the highest at $4.36.

In California, the lowest average price was $4.24 in Fresno. The average statewide for a gallon of regular was $4.33, up about 16 cents.