Refinery problems or hurricanes can halt the typical autumn price decline temporarily by reducing gasoline production. For example, a reported outage at a refinery in Eastern Canada that supplies the Northeast with gasoline is likely to push the price at the pump slightly higher in some markets over the next few days.
But by late October prices are usually well on their way lower.
Last year, the national average fell 28 cents per gallon between Sept. 1 and Dec. 31. This year, gasoline had a head start. It entered September at its lowest level for the beginning of the month in four years - and the price of crude oil was rapidly heading lower.
The drop in global crude oil prices is a surprise. Despite increasing violence and turmoil in the Middle East, the world's most important oil-producing region, the global price of oil has fallen to $97 a barrel, close to its lowest level in more than two years.
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That's partly because new technology has allowed U.S. drillers to consistently increase production from fields in North Dakota and Texas, adding to global supplies. At the same time, world demand is not growing as much as anticipated because of slower economic growth in China and Europe.
The increase in domestic supplies is also helping avoid dramatic spikes in gasoline prices, which economists say is more damaging to consumer confidence than prices that rise gradually. This year, the national average peaked in April at $3.70 per gallon. Last year, the peak was $3.79, and the year before it was $3.94.
The national average for gasoline is not likely to fall all the way to $3 because of a number of factors. Some state gasoline taxes have increased. Loyalty programs that offer discounts to members at many stations keep listed prices higher than what drivers actually pay. And some states have adopted regulatory rules that will probably add a few cents per gallon, Kloza said.
He predicts the national average will end the year somewhere between $3.15 and $3.25 per gallon.