Diesel prices saw their largest week-to-week change of 2017 and fell to the lowest national average of the year during the week ending March 20, according to the Department of Energy’s weekly report.

Prices fell 2.5 cents during the week to $2.539 per gallon nationwide. Fuel prices fell in all regions, with the most significant decrease coming in the Gulf Coast region, where prices dropped by 3.9 cents.

The nation’s most expensive diesel can be found in California at $2.928 per gallon, followed by the Central Atlantic region at $2.738 per gallon.

The cheapest fuel can be found in the Gulf Coast region at $2.38 per gallon, followed by the Midwest at $2.464 per gallon.

Prices in other regions, according to the DOE, are:

New England – $2.622
Lower Atlantic – $2.498
Rocky Mountain – $2.59
West Coast less California – $2.702
ProMiles’ numbers during the same week had diesel prices falling by 2.6 cents to $2.486 per gallon.

According to ProMiles’ Fuel Surcharge Index, the most expensive diesel can be found in California at $2.865 per gallon, and the cheapest can be found in the Gulf Coast region at $2.393 per gallon.