Since then, the prices of oil and gasoline have just kept rising. Over the last three months, the average retail price of unleaded regular gasoline was $3.75 a gallon, nearly 65 cents higher than the average price in the first quarter of the year, according to the Oil Price Information Service. The research group has estimated that Americans are now spending $1.6 billion a day on gasoline, which would make July the first month ever when the American gasoline bill would top $50 billion.

Tom Kloza, the group’s chief oil analyst, predicted that a barrel of oil would reach $155 by August and that retail prices for gasoline would rise to $4.25 to $4.50 a gallon for unleaded regular.

“The firecrackers are going off in the oil market and it will burn the U.S. consumers this holiday weekend,” Mr. Kloza said. He added that truckers stood to suffer most, noting that diesel prices rose 13 cents a gallon Wednesday afternoon in response to the Energy Department report.

“Diesel is the bullet with the most acceleration at the moment,” he said. “ You are going to see a lot of bankruptcies in the trucking business.”

Pushing up the price of crude are any number of factors, including continued instability in Nigeria, a partial strike at Venezuela’s state oil company and reports that Israel is considering an attack on Iran. Yet another reason for oil’s price climb came with the Energy Department’s weekly statistical bulletin, which showed that crude oil stocks had slipped by nearly 2 million barrels to below 300 million barrels.

Analysts say that level is psychologically important because crude oil stocks as recently as last year were above 350 million barrels. The inventory level was the lowest since January, and below what most analysts had expected. The crude oil inventory figure was 54 million barrels below a year ago, and nearly 22 million barrels below the five-year average, according to tabulations by Barclays Capital.

There was also some modestly good news in the report. Gasoline inventories rose 2.1 million barrels to 210.9 million barrels, an indication that gasoline demand is slackening a bit as drivers car-pool, buy more efficient cars, and use more mass transit when it is available.