U.S. retail gasoline prices increased for third week in a row, jumping 1.6 cents a gallon at the pump over the last week to $1.112, according to a Jan. 7 report from the Department of Energy. Even with the recent increases, the price of regular unleaded gasoline is still down 31 cents from a year ago, according to the department's weekly survey of more than 800 service stations. Fuel prices have increased in each of the last three weeks after declining for 13 weeks straight following the Sept. 11 terrorist attacks on the United States. The higher gasoline costs reflect the recent rise in crude oil prices and the increase in petroleum demand during the just-ended holiday driving period, according to industry analysts. The national average price for cleaner-burning reformulated gasoline, sold at about one-third of the stations in cities and smoggier areas, was up 2 cents to $1.117 a gallon. Prices on the West Coast increased 2 cents, giving the region the most expensive gasoline in the nation at $1.151 a gallon. Motorists in the Gulf Coast states had the most inexpensive fuel, with the average price in that region increasing 1.9 cents to $1.055. San Francisco kept the dubious honor of being tops among major cities in fuel costs, with gasooline prices rising 0.2 cents to $1.277 a gallon. Houston again had the best deal for drivers, although petrol was up 2.6 cents to $1.018 a gallon. The nationwide average price for diesel fuel dropped 0.1 cents to $1.168 a gallon, down 35 cents from a year ago. Truckers in New England paid the most for diesel fuel at $1.291 a gallon, up 0.2 cents. The Rocky Mountain states had the lowest-priced diesel at $1.128 a gallon, up 0.4 cents.