RIVERSIDE, Calif. -

The average price of a gallon of self-serve regular gasoline in the Inland Empire rose four-tenths of a cent Friday to $4.269, its highest amount since March 5, 2013.

   The average price in Riverside and San Bernardino counties is nine- tenths of a cent more than a week ago, 26.5 cents higher than a month ago and 35.4 cents above what it was one year ago, according to figures from the AAA and Oil Price Information Service.

   ``Gas prices remain at very high levels at least partly due to the increased cost of ethanol and extended refinery maintenance,'' said Jeffrey Spring of the Automobile Club of Southern California.

   ``It's hard to say when significant relief will arrive because wholesale prices continue at high enough levels to keep pump prices well above $4 a gallon.''