Diesel prices gained nearly a nickel this week, kicking off the month of May at its highest level since October 2008

, according to weekly figures released by the U.S. Energy Information Administration. Diesel rose to a national average of $3.122 a gallon, its fifth straight weekly increase.

Last month, diesel prices rose above $3 a gallon for the first time since November 2008. Over the last five weeks, trucking's main fuel has gained 18.3 cents. This week's average was 93.7 cents higher than the same week last year.

The West Coast and Central Atlantic regions had the highest prices this week, averaging $3.243 and $3.238 a gallon, respectively. The Lower Atlantic and Gulf Coast saw the lowest prices, at $3.079 and $ 3.083 a gallon, respectively.

Crude oil prices were up to $86.19 a barrel on the New York Mercantile Exchange Monday, the highest in three weeks, according to Bloomberg. The news service attributes the increase to the April 2010 Manufacturing ISM Report On Business, released Monday. The ISM Index, which measures manufacturing activity, was at 60.4 percent in April, its fastest growth rate since June 2004.

"Overall, the recovery in manufacturing continues quite strong, and the signs are positive for continued growth," said Norbert Ore, chair of the Institute for Supply Management Manufacturing Business Survey Committee.

Meanwhile, analysts expect oil to reach as high as $100 a barrel this summer, as a rapid recovery in developing countries in Asia should boost demand, according to reports by Time.com.