The U.S. average retail price of regular gasoline decreased four cents to $3.55 per gallon as of Sept. 16, according to the Energy Information Administration (EIA). That price is 33 cents lower than last year at this time, the EIA reports in the Sept. 18 issue of This Week in Petroleum.

Prices were down in all regions except the West Coast, where the price increased 10 cents to $3.90 per gallon, the largest one-week increase since May 13, 2013. The largest decrease came in the Midwest, where the price was $3.49 per gallon, nine cents lower than last week. The Gulf Coast price was eight cents lower at $3.30 per gallon. On the East Coast the price was $3.53 per gallon, a drop of six cents, and the Rocky Mountain price was $3.61 per gallon, a decrease of two cents.

The national average diesel fuel price decreased a penny to $3.97 per gallon, 16 cents lower than last year at this time. Prices fell in all regions except the Rocky Mountains, where the average price increased one cent to $3.94 per gallon. The East Coast, Midwest, and Gulf Coast prices all decreased one cent, to $3.98 per gallon, $3.96 per gallon, and $3.89 per gallon, respectively. The West Coast price is lower by less than a penny to remain at $4.14 per gallon.