U.S. retail diesel prices trickled down last week for the first time in nearly four months, the Department of Energy reported, but analysts said it was unlikely the trickle would start a downward trend at the pumps.

The average price of U.S. retail diesel rose for the 15th consecutive week, bumping up another 3.7 cents to $3.908 a gallon, nearly $1 higher than the comparable week of last year, according to the Department of Energy.

Oil fell to a two-week low Monday to less than $100 a barrel in part due to concerns that Japan’s big earthquake Friday will hurt growth and reduce fuel demand in that country’s economy, the world’s third-largest, Bloomberg reported.

Fuel prices have now jumped so high that we all need to pay close attention. Not that we can do much about these skyrocketing prices, except pay and grumble.

U.S. retail diesel prices shot up another 15.5 cents last week in the largest one-week increase in nearly three years, as the national average price reached $3.871 a gallon, the highest since October 2008, the Department of Energy said.

Gasoline’s national average price jumped 33 cents in the past two weeks to an average $3.51 a gallon, according to the latest Lundberg Survey of filling stations released Sunday.