Diesel prices gained 2 cents this week, in the fuel's fourth weekly hike in a row.
After last week's 4.3-cent boost, the national average price of diesel landed at $2.924 a gallon, according to the Department of Energy.

Over the last four weeks, diesel has increased 16.8 cents. Prior to its upward trend, diesel fell 12.3 cents over five weeks. This week's average is 90.7 cents higher than the same week last year.

Prices averaged $3.065 in California, where diesel was the highest. The Central Atlantic region also had high prices, averaging $3.055 a gallon. The Midwest and Lower Atlantic regions came out with the lowest averages, both at $2.895 a gallon.

Meanwhile, oil prices reflected a stronger dollar and investor worries over energy demand, according to reports by the Associated Press. The news service said crude oil ended trading Monday at $79.80 a barrel on the New York Mercantile Exchange. Crude prices haven't slipped below $80 in almost two weeks, the AP said. Last week, oil hit an eight-week high.