This week, fleet operators will get some relief as diesel and gas prices drop. Oil prices also fell this week due to easing tensions over Iran.

Diesel prices dropped the most since December 2011 this week, according to the Energy Information Administration's weekly fuel update. The nation's average price dropped by 2.1 cents to $4.127 a gallon. Prices fell for every U.S. region, and Midwest prices dropped the most, by 3.4 cents to $4.021.

Gasoline prices leveled off this week, dropping an average of 0.2 cents to a national average of $3.939 a gallon, but analysts say we'll see higher prices closer to Memorial Day. The Midwest saw the biggest decrease, a 4.5-cent drop to $3.860 a gallon.

Benchmark crude dropped 4 cents to $102.79 a barrel and Brent crude lost $2.72 to $118.49 in London. Analysts say the decline is due to easing tensions after a meeting in Istanbul this week over Iran's nuclear program. Although the meeting didn't result in a concrete agreement, analysts say that as long as negotiations continue, there is a reduced chance of fighting in the Persian Gulf.

Click here for the Energy Information Administration's weekly fuel update.