Diesel prices are up this week after a three-month-long downward trend, but gasoline prices continue to decline. Oil prices rose on Monday due to concerns that a labor dispute in Norway could lead to a complete shutdown of the country's oil production.

The national average price of diesel is up 3.5 cents this week to $3.683 per gallon, according to the Energy Department's weekly report. The New England and Rocky Mountain regions were the only two that experienced price decreases. With prices up 5.8 cents, the Midwest saw the highest price increase for diesel.

Gasoline prices continued to fall this week, the DOE reports, dropping by 8.1 cents to $3.356 per gallon. Gas prices are at their lowest since January.

Light, sweet crude for August delivery settled at $85.99 a barrel on the New York Mercantile Exchange, up $1.54. Brent crude on the ICE futures exchange was up $1.79, or 2.2%, to $99.98 a barrel.

Affecting oil prices this week is a strike by Norwegian petroleum workers, who are at a standoff with oil companies over the terms of their retirement package. The companies are threatening to halt all production and to lock out the workers if a deal isn't reached. Norway is the world's eighth-largest oil exporter. Currently, the country pumps about 2 million barrels per day, roughly equivalent to 2.2% of global supply.