Surveys indicate that over the past two weeks the average price of gasoline in the United States jumped 15 cents for a national mean price of $3.62 per gallon (self-serve, regular.)

These figures were released on Sunday, May 4 by the Lundberg Survey, which is conducted biweekly. The spike in prices was virtually identical to the previous two weeks during which the per gallon cost rose 16 cents.

On Monday, statistics compiled by AAA, indicated, however, that for the fourth day in a row the per gallon price of regular unleaded actually dropped, bringing the level from a record $3.623 last week to $3.611.

AAA updates its survey material on a daily basis and makes the computations based on data gathered at approximately 80,000 filling stations dispersed across the United States. The numbers are gathered and crunched by the Oil Price Information Service.

Crude oil opened at more than $117 a barrel on Monday with continued concerns about global supplies after renewed attacks on oil installations in Nigeria. Even in the face of a strengthening dollar, however, most analysts agree the price of gas will continue to rise, especially with the advent of the busy summer season.

According to the Lundberg survey, the lowest price for gas in the U.S. was in Cheyenne, Wyoming at $3.39 while people in San Francisco paid the most at $3.95 per gallon, just shy of the $4 per gallon mark consumers are expected to be paying before the end of the summer.