The price of regular gasoline dropped 2 cents a gallon in California during the week ended Oct. 16, but diesel fuel prices increased 4 cents a gallon during the period, according to the California Energy Commission.

Because of California’s emission-control standards are tougher than most states, gasoline and diesel fuel have to be specially formulated for use in the state.

During the week of Oct. 16, the price of regular gasoline in California averaged $1.81 a gallon, while the nationwide averaged climbed 4 cents to $1.54 a gallon.

Meanwhile diesel fuel averaged $2.01 a gallon in northern California during the week of Oct. 16. It averaged $1.91 a gallon at truck stops in central California and $1.90 a gallon in southern California.