By Tom Doggett

The national price for regular unleaded gasoline is $2.91 a gallon, the cheapest since October 29, 2007, but still up 9.1 cents from a year ago, the department's Energy Information Administration said in its weekly survey of service stations.

The average pump price has fallen 57 cents a gallon in the last two weeks because of cheaper crude oil and lower petroleum demand due to a weak economy.

Falling gasoline prices act like a tax cut for consumers, shaving about $30 off the fill-up cost for the average big vehicle from the record $4.11 a gallon for gasoline in July.

The savings would give a family an extra $1,000 a year, according to government estimates.

In the EIA's weekly survey, gasoline was the most expensive on the West Coast $3.28 at gallon, down 14.6 cents. San Francisco had the highest city price at $3.49, down 11.3 cents.

The Gulf Coast had the lowest regional price at $2.73 a gallon, down 25.6 cents. Cleveland had the lowest city pump price, down 19.9 cents at $2.70.

The EIA also reported gasoline prices were down 9.4 cents at $3.34 in Los Angeles; down 26 cents at $3.20 in Chicago; down 27 cents at $3.09 in Seattle; down 30 cents at $3.08 in Miami; down 22 cents at $2.94 in New York City; down 30 cents at $2.93 in Denver; down 22 cents at $2.84 in Boston and down 27 cents at $2.76 in Houston.

Separately, the average price paid for diesel fuel fell 17.7 cents to $3.48 a gallon, also the lowest since mid February, but 39 cents higher than a year earlier, the EIA said.

The New England states again had the most expensive diesel at $3.73 a gallon, down 16.3 cents. The West Coast had the cheapest diesel at $3.43, down 18.9 cents.

(Reporting by Tom Doggett; Editing by Marguerita Choy)