RIVERSIDE, Calif. -

The average price of a gallon of self-serve regular gasoline in the Inland Empire rose to its highest amount since Sept. 23 today, increasing 1.7 cents to $3.978.

   The average price in Riverside and San Bernardino counties has risen 23 of the past 24 days and is 4.4 cents more than one week ago and 26.1 cents higher than one month ago, according to figures from the AAA and Oil Price.  However, the average price is 21.9 cents less than one year ago.

   The average price has risen 21.8 cents over the past 24 days, including nine-tenths of a cent on Wednesday.

   The rising prices have been attributed to the start of production of the more expensive summer blend of gasoline, causing supplies of winter blend gasoline to drop.