Ultra-low-sulfur diesel’s lower energy content will force truckers to buy more fuel to run the same number of miles, driving fuel expenses up — a cost they can’t recoup through surcharges, trucking executives and engine manufacturers said.

Petroleum-industry representatives have set up a consortium to test ultra-low-sulfur diesel that they said would give fuel retailers a potential defense if they are found to be selling ULSD that is over the government’s sulfur limit.

Special “boutique” fuel blends produced to meet local air-quality requirements did not contribute to the recent supply shortages and dramatic nationwide run-up of fuel prices, according to a task force of federal and state officials.

A measure to reduce diesel emissions in California by authorizing local air districts to regulate emission sources won approval in the state’s Senate Transportation Committee last week.

The Engine Manufacturers Association said a new emissions-testing program for heavy-duty diesel vehicles is nearing completion and will become mandatory for all engine manufacturers next year.

With the deadline for beginning retail sale of ultra-low-sulfur diesel four months away, fuel transporters and retailers said they would closely monitor their distribution systems for sulfur contamination as refiners begin to produce and distribute more of the new fuel.

The Environmental Protection Agency’s deadline for U.S. fuel refiners to begin making ultra-low-sulfur diesel was June 1, but not all refiners said they would make the fuel immediately.

American Trucking Associations said it estimated that the June 1 transition to ultra-low-sulfur diesel would increase the cost of trucking’s main fuel by at least 5 cents a gallon, while lowering the energy output of diesel by 1%.

American Trucking Associations said it opposed a bill before the California legislature that would require all diesel fuel sold in the state to contain at least 2% biodiesel by 2008 and at least 5% biodiesel by 2010.

Beginning June 1, trucking companies that use in-house central refueling facilities will be required to label their diesel pumps as either ultra-low-sulfur diesel or low-sulfur diesel, said the Environmental Protection Agency.