Gas prices continue to decline.

The Lundberg Survey of fuel prices, released today, finds the average U.S. price of a gallon of regular gasoline has dropped 8.5 cents over the past two weeks to $3.75.

Midgrade costs an average of $3.93 a gallon, and premium is $4.06.

Diesel dipped three cents to $4.15 a gallon.

Of the cities Lundberg surveyed in the lower 48 states, Tulsa, Okla., has the nation’s lowest average price for gas at $3.26. San Francisco has the highest at $4.51.

A separate survey by the auto club AAA puts the national average price for a gallon of regular self-serve gasoline at $3.72 per gallon as of Friday. That’s nine cents below week-ago prices and 13 cents below month-ago prices.

However, AAA says gas prices remain 25 cents above year-ago prices and 39 cents below the record high set back in July 2008.