Hawai'i diesel prices fell 3.7 cents last week, but the decline provided little consolation for local truck and bus owners who pay the highest prices for the fuel in the nation.

Prices for diesel were $3.892 a gallon, according to AAA Hawaii's Daily Fuel Gauge report on Friday. The prices are well under the record $5.519 a gallon paid for the fuel during last year's market spike, but users still grumble about local prices not falling as much as the Mainland.

"We need diesel to do our jobs and it's tough when prices are that high," said Gareth Sakakida, managing director for the Hawaii Transportation Association, a trade group that represents many of Hawai'i's trucking and bus companies.

"With the environmental regulations to the refining of diesel now, I know it's a more expensive process, but the way it's skyrocketed over the past three years, it's just shocking to everyone."

Like gasoline, a number of factors, including the cost of crude oil, refining, marketing, transporting and retailing, affect the cost of diesel, according to the U.S. Energy Information Administration. Also factored in is demand, which earlier this year fell as the economy slipped into recession.

Nationally, the price of diesel fell about 45 percent over the past year, or $2.14, to $2.627 on Thursday.

Hawai'i's prices have fallen the least of any state during the past year, declining $1.451, or 27 percent.

The state's average diesel price is $1.265 more than the national average, and Hawai'i and Alaska are the only states where diesel costs more than $3 a gallon.

Last Thursday, there were 18 states where the price of diesel was less than a gallon of regular gasoline.

The Western States Petroleum Association, a trade group that represents oil companies and refiners, said it was not aware of specific factors for Hawai'i's diesel prices aside from the state having higher price volatility with its two small refineries.

One partial reason for the higher prices here is the amount of taxes paid at the pump. Hawai'i's 70.5 cents of taxes for diesel is the nation's highest and is nearly 20 cents higher than the national average of 50.8 cents a gallon.

Sakakida said local companies have had no choice but to try and pass on the prices they're paying for diesel. But that's been difficult in the current economy, he said.

"We're not discretionary users of fuel," Sakakida said. "We have to make the runs, and we have to pay the price."