According to figures released by the Energy Department Nov. 18, the national average cost of diesel dipped to $1.405. The sag in price marks the fourth straight week the cost of diesel has dropped.

The lowest prices nationally are in the Gulf Coast region. Diesel there costs $1.346 per gallon on average - down from $1.371 last week. The highest average price is in California. Fuel there is $1.524 per gallon - down from $1.541. The remaining regions' prices per gallon are as follows: East Coast, $1.394; New England, $1.492; Central Atlantic, $1.485; Lower Atlantic, $1.347; Midwest, $1.406; Rocky Mountain, $1.461; and West Coast, $1.50.

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.