The annual springtime increase of U.S. gasoline prices could lead to a national average price of $2.50 per gallon, which could make a full tank for an SUV cost $65 or more. California, where gas prices are usually highest, could be averaging almost $3 a gallon by June.

GasPriceWatch.com says the national average for unleaded gas is $2.30 a gallon, 40 or 50 cents higher than last year. California gas prices are averaging $2.50 per gallon, compared to $2.10 in April 2004. By summer, Americans could be spending $5 billion more per month on gasoline than they did last year.

A Goldman Sachs analysis of how high prices would have to go to spur changes in American driving behavior predicted that oil could reach $135 a barrel by 2008, which would lead to average gas prices of about $4.30. That price is considered high enough to substantially reduce gasoline consumption.