The average price for all grades of gasoline nationwide has fallen nearly 4 1/2 cents per gallon in two weeks because of a drop in crude oil prices (search) and slightly lower demand, an industry analyst said Sunday.

The average retail price for all three grades dropped 4.46 cents to $2.27 per gallon between April 8 and Friday, said Trilby Lundberg, who publishes the semimonthly Lundberg Survey (search) of 7,000 gas stations around the country.

The most popular grade, self-serve regular, was priced at $2.24 a gallon, while customers paid $2.34 for midgrade. Premium averaged $2.44 a gallon for the period.

The drop comes after an average 19-cent jump in overall gas prices during the last survey, taken between March 18 and April 8.

"This is the first significant price drop in retail gasoline this year," said Lundberg. "It's not possible to quantify, but demand for gasoline is surely being dampened by high prices to a level lower than it would have been."

Lundberg also said the cost of crude oil fell several dollars last week, triggering the dip in pump prices.

She predicted that gasoline prices would plateau and or decrease in the coming weeks, but that any dips would be erased in the long-term by increased demand from summer travel and an increase in refining costs.

The highest average gas price in the nation for regular unleaded was $2.64 a gallon in San Francisco (search). The lowest price was $2.04 in Tulsa, Okla.