( CNN ) -- Barring a steep drop in crude prices , U.S. motorists can expect to see gas prices exceeding $ 3 per gallon , if they are not seeing such prices already , according to a new survey of filling stations . The latest Lundberg Survey of cities in the continental United States was conducted Friday . It showed the national average price for a gallon of self-serve unleaded gasoline at $ 2.91 , an increase of 3.9 cents from the last survey two weeks earlier , survey publisher Trilby Lundberg said . `` It is once again crude oil at work , '' Lundberg said . A resurgence in crude prices resulted in the price per barrel increasing nearly $ 8 per barrel . At $ 89 per barrel , crude is at a 25-month high . The rise in prices predicted by Lundberg is based on the necessity for gas retailers to reflect an increase in the wholesale price of gas at the pump . Profit margins on a gallon of gas for a retailer fell by about half in the last two weeks , Lundberg said . The retail margin for retail is less than six cents per gallon . Retailers will have to raise prices at the pump to make up for it . `` We may easily pay three dollars per gallon or more by Christmas , '' Lundberg said . Gas prices in this survey were nearly 28 cents higher than in December a year ago . The Lundberg Survey sampled prices at about 2,500 gas stations . The highest average price in the continental United States was in Long Island , New York , at $ 3.21 per gallon . The lowest price was in Denver , Colorado , at $ 2.61 . Average per-gallon prices in other cities : . Albuquerque , New Mexico : $ 2.75 . Atlanta , Georgia : $ 2.84 . Baltimore , Maryland : $ 2.90 . Chicago , Illinois : $ 3.09 . Miami , Florida : $ 2.96 . Minneapolis , Minnesota : $ 3.03 . Philadelphia , Pennsylvania : $ 3.02 . Portland , Oregon : $ 2.99 . San Francisco , California : $ 3.19 .
Gas prices increase by nearly four cents . A gallon of gas is nearly 28 cents higher than last year . Prices could reach $ 3 per gallon by Christmas , survey publisher says .