During the week ending May 11, diesel fuel prices increased 2 cents per gallon. Over the past four weeks, diesel fuel has now risen 12 cents a gallon.

The Energy Information Administration (EIA) reported that April crude oil spot prices hit its highest monthly average so far this year. Reasons behing the increase, according to the EIA, are indications that global oil demand is picking up, evidence that U.S. tight oil production could drop in the next few months, and the growing risk of unplanned supply outages in the Middle East and North Africa.