According to figures released by the Energy Department Dec. 9, the national average cost of diesel this week is $1.405 per gallon, down slightly from last week, when diesel was $1.407.

The lowest price nationally is in the Gulf Coast region. Diesel there costs $1.345 per gallon on average, down slightly from $1.37 last week. The highest average prices were in California, where fuel is $1.496 per gallon; in the Central Atlantic, where the price is $1.491; and in New England, where the price is $1.492.

The remaining regions' prices per gallon are as follows: East Coast, $1.404; Lower Atlantic, $1.358; Midwest, $1.408; Rocky Mountain, $1.444; and West Coast, $1.478.

The Department of Energy reports the average price of self-serve fuel each week. Prices are based on a survey of 350 diesel service centers nationwide and include taxes.