The old rules of supply and demand apparently don’t apply to petroleum anymore. Gasoline consumption rates are down, supplies are up, yet pump prices continue to rise.

Triple-A-Iowa spokeswoman Rose White says Iowa continues to see its gas prices creep upward toward the $4 mark, despite a drop in the cost of crude. White says, "Crude oil prices in the U.S. commodities market retreated nearly nine-dollars a barrel this week after reaching a new record high just prior to the July 4th holiday where they were trading above $145 a barrel."

White says Iowa motorists are taking more long trips now that summer’s in full swing, though she notes travel for the Independence Day holiday was down nationwide.

White says self-service regular unleaded is averaging $3.97 in Iowa. A year ago, the statewide average was $3.16 a gallon. Diesel fuel in Iowa is averaging $4.67 a gallon. Nationwide, Alaska reports the highest gas prices at $4.63, while Missouri and South Carolina are tied for the lowest price at three-91. For more information on fuel prices, log on to the AAA website .