SAN DIEGO, CA — The average price of a gallon of self-serve regular gasoline in San Diego County dropped Monday for the 21st consecutive day, falling a half-cent to $4.029, its lowest amount since Sept. 28.

The average price has dropped 17.7 cents over the past 21 days, including a half-cent on Sunday, according to figures from the AAA and Oil Price Information Service. The decreases follow a run of 19 increases in 21 days, which pushed the average price to its highest level since July 20, 2015.

The average price is 8.9 cents less than one week ago, but 2.8 cents more than one month ago and 21 cents higher than one year ago.