Diesel is up again this week with a 4-cent increase to $4.094 per gallon from $4.051 per gallon, according to the Energy Information Administration's gas and diesel fuel update.

Diesel prices haven't been this high since May 2011, and, a year ago, the average diesel price was 22 cents less than what it is now.

Average U.S. gas prices are up 7 cents from a week ago to $3.793 per gallon from $3.721 per gallon. A year ago, prices were 27 cents lower than they are now. The Rocky Mountain region saw the largest increase at 13 cents, and the Midwest was close behind with a 12-cent increase.

Light, sweet crude for April settled 2 cents higher at $106.72 a barrel on the New York Mercantile Exchange. Brent crude on the ICE futures exchange was recently 39 cents higher at $123.71 a barrel.

The Wall Street Journal reports that oil prices are up 8.7% since the beginning of February due to concerns over Iran and improving economic conditions in the U.S. and abroad that analysts predict will increase demand for crude.

The sharp rise in oil prices in February is partly a result of apprehensions about a potential Israeli military strike on Iran and disruptions of Iran's 3.5-million-barrel-a-day oil production.