On-highway diesel prices rose by 10 cents last week, more than double the previous week's increase of 4.4 cents. Prices have now topped $4 per gallon on the national average and in every major region.


The average price per gallon is over a dollar more than one year ago.

In contrast, oil futures fell back below $110 a barrel after last week's 30-month high as traders grow concerned that rising prices are beginning to weigh on demand. Light, sweet crude for May delivery settled $2.87, or 2.5 percent, lower at $109.92 a barrel on the New York Mercantile Exchange after hitting a fresh multiyear high of $113.46 earlier in the session. Brent crude on the ICE futures exchange dropped $2.63 to $124.02 a barrel.

The sharp rise in oil prices last week has investors rethinking whether demand is sustainable amid a global economy still in recovery, which is only expected to grow by 4.4 percent this year according to the IMF. The U.S. is forecasted to grow 2.8 percent.

Worries about demand represent a sharp turn from the concerns over supply disruptions that have driven oil futures up by nearly 20 percent this year. The possibility of an end to hostilities in Libya after African Union mediators arrived to broker a cease-fire spurred an early pullback in oil prices.