The Department of Energy's Energy Information Administration has lowered its price forecasts for on-highway diesel to just under $3 a gallon for 2010 and $3.11 for 2011

, according to the most recent Short-Term Energy Outlook.

At the beginning of May, the EIA announced it had raised its predictions for diesel to $3.05 a gallon in 2010, and $3.20 in 2011. The most recent figures are closer to April's forecasts.

National diesel prices have fallen 18.1 cents over the last four weeks, slipping 3.4 cents this week to an average of $2.946 a gallon this week. Prior to the declines, diesel had gained 18.8 cents.

The EIA said it expects oil prices to average about $79 a barrel during the second half of this year and rise to $84 by the end of next year, lower than last month's forecasts. In the last outlook, EIA said oil would average about $84 a barrel during the second half of this year and $87 by the end of 2011.

"Uncertainty about economic growth in China and in the Euro zone has continued to weigh on oil markets, and declines in equity markets have led to fears that the economic recovery may not progress as fast as had been hoped," the EIA said.