For the sixth straight week, average retail gasoline prices have dropped nationwide, falling below $2.30 a gallon for the first time since early August.

The federal Energy Information Administration said Monday that U.S. motorists paid $2.296 cents a gallon on average for regular grade last week, a decline of 8 cents from the previous week. Pump prices are still 32.7 cents higher than a year ago.

Average retail prices peaked at $3.07 a gallon in early September, a reflection of the extreme tightness in the market following Hurricane Katrina, which knocked out refineries in the Gulf region, as well as pipelines that deliver fuel to the East Coast and Midwest. Prices have since retreated because of the recovery of oil production and refining facilities, increased imports from Europe and a slight moderation of demand.

Gasoline prices were most expensive last week on the West Coast, averaging $2.547 per gallon, and cheapest in the Midwest, averaging $2.178 per gallon.

One of the key factors underpinning the high price of gasoline is the cost of crude oil, which has been elevated by strong demand, tight global supplies and geopolitical uncertainties.

Crude-oil futures settled Monday at $57.69 on the New York Mercantile Exchange. That is about 20 percent higher than a year ago.