Diesel and crude oil prices continue to plummet, with the national average price of a gallon of diesel dropping below $3.50 for the first time since February -- but OPEC is not taking low oil prices sitting down.

The U.S. national on-highway average for diesel as reported by the U.S. Energy Information Administration Monday was 3.482. The average diesel price is now only 38.8 cents per gallon more than it was a year ago.

The highest average prices were seen in the New England region at $3.729; the lowest on the West Coast at $3.433.

Crude oil prices dropped below $70 a barrel on the New York Mercantile Exchange last week, the lowest prices since June 2007 and a 50-percent drop from their record levels this July.

But OPEC, the cartel representing oil-producing countries, plans an emergency meeting later this week to address the situation. According to published reports, OPEC may cut production by 1 million to 2 million barrels a day in stages at an Oct. 24 meeting to stabilize prices. While there's a consensus among the group's members to cut output, there's no agreement on the size of the reduction, reports Bloomberg.com, quoting an interview by OPEC president Chakib Khelil on Algerian television. Reuters reports that OPEC members have said they would be more comfortable with prices around $80-$90 a barrel.

Also in fuel news, in Canada, a diesel fuel shortage in Manitoba, Saskatchewan and Alberta could last several more weeks as refineries undergo maintenance, according to Reuters. Supplies in have been tight as three refiners have been doing maintenance work at their plants.