National on-highway diesel prices rose again after falling slightly last week, according to the Energy Information Administration.

The national average price rose 2.6 cents last week to $4.124. Last week the price decreased by seven-tenths of a cent.

Prices are still north of $4 per gallon in every region. California was most expensive at $4.465. While Gulf Coast prices are still the lowest at $4.06, it atypically had the highest regional gain of 3.6 cents.

Crude for June delivery declined 41 cents on Monday, or 0.4 percent, to $113.52 a barrel on the New York Mercantile Exchange after settling Friday at its highest level since September 2008. Oil rose $1.24 over last Monday.

It is unclear how the death of infamous terrorist Osama bin Laden, which the United States has pursued for over a decade, will affect oil prices. After the initial announcement by President Obama on Sunday, prices fell in East Asian markets. Some analysts expect bin Laden's death will cause global terror to decrease with a corresponding decrease in oil prices. Others say that if his death causes more unrest, particularly in bin Laden's home country of Saudi Arabia, the world's largest oil exporter, prices could rise dramatically.

However, a more immediate issue is the apparent cool-off in U.S. manufacturing. The sector posted its 21st consecutive month of expansion last month but the Institute for Supply Management's Manufacturing Index dipped to 60.4 percent from 61.2 percent in March. Such a slow down would damage oil prices.