The average U.S. price of regular-grade gasoline dropped by 6 cents over the past two weeks to $3.41 per gallon.

Industry analyst Trilby Lundberg of the Lundberg Survey said Sunday that prices have been falling for a month due to lower crude oil costs.

Nationwide, the highest average price for regular-grade gas is in the San Francisco Bay Area, at $4.77 per gallon. The lowest average is in Houston, at $2.83 per gallon.

According to the survey, the average price of diesel is $3.65 a gallon, down 3 cents since Dec. 3.