The average price of a gallon of diesel fuel in the United States for the week of January 28, 2019 is $2.965. Even though the price in California was slightly down from the previous week, it continues to be the highest in the country at $3.726 per gallon. The Gulf Coast Region remains the most economical area of the Union to purchase diesel fuel. The average price in this region is $2.789 per gallon. Seven regions showed a slight decrease in price, while only three increased. Hopefully, this trend will continue in 2019.