For the third week in a row, the average price of a gallon of diesel fuel decreased, according the latest numbers from the Energy Department.

The price of a gallon of on-highway diesel fuel dropped by a slight 1.3 cents, settling at $2.485 per gallon. Diesel fuel is still much cheaper than it was at this time last year and is down $1.138 per gallon year-over-year.

The largest drop in prices by region was in the Midwest, decreasing by 2.4 cents for the week. While prices were down in most regions, there was a barely register-able increase in California of 0.4 cents per gallon.

The price of a gallon of regular gasoline was essentially flat during the same period, with a national average decrease of 0.4 cents. The price is 76.9 cents cheaper than the same week a year ago. The largest decrease was in the Rocky Mountain region, dropping by 6.2 cents but it was offset by an increase of 4 cents in the Midwest.

Crude oil prices fell in stock market trading on Monday continuing the year-long narrative of increased supplies outweighing a weakened demand, according to a Wall Street Journal report.

Despite a weaker than expected Chinese economy and awareness that U.S. oil production was outstripping demand, prices slid further on word that OPEC's production output has actually increased in recent months.