RIVERSIDE, Calif. -

The average price of a gallon of self-serve regular  gasoline in the Inland Empire rose 1 cent Friday to $3.81, its highest amount  since Oct. 9.

   The average price in Riverside and San Bernardino counties has risen 17 of the past 18 days and is 7.1 cents more than one week ago and 19.1 cents higher than one month ago, but 46.4 cents less than one year ago, according to figures from the AAA and Oil Price Information Service.

   The average price has risen 21.3 cents over the past 18 days, including 1.8 cents on Thursday.

   The rising prices are the result of the annual refinery maintenance season when supplies of winter blend gasoline drop as refineries start  production of the more expensive summer blend, according to the Automobile Club of Southern California.

   ``Los Angeles wholesale gasoline prices dropped in the last week and at this time, there's not much more momentum for further increases at the pump, although as we know from past spring seasons, that can change very quickly,'' said Jeffrey Spring of the Automobile Club of Southern California.