Hawai'i diesel prices hit a record high of $3.49 a gallon this week, crimping the fuel budgets of commuters, construction companies, tour bus operators and charter boat captains.

Unlike local gasoline prices, which have fallen for the past four weeks, diesel prices have risen over the past month. The average is now about 30 percent higher than a year earlier in the state, according to the American Automobile Association's Daily Fuel Gauge report.

"In September my fuel bill went up by about $1,500," said Sonny Rivera, owner of Aikane Sport Fishing at Hickam Air Force base. "It got to the point where I wasn't even looking at the prices."

Rivera, who had been paying a fuel tab of about $4,000 a month, raised the price for his basic eight-hour charter to $640 from $575 last month because of surging petroleum prices.

"A lot of the commercial charter fishing fleet is having the same problems," said Rivera, who is looking at lower income this year versus last year because of higher fuel costs.

U.S. retail prices for diesel spiked in October as production didn't rise fast enough and demand increased from farmers harvesting crops, according to the U.S. Energy Information Administration.

Strong demand internationally for diesel also may have cut into imports of the fuel, the energy agency said in a report last month. Diesel prices hit a high nationally on Oct. 24, according to AAA.

Diesel prices aren't regulated under Hawai'i's gas cap law that went into effect Sept. 1. The law limits how much wholesalers can charge for gasoline.

Gasoline prices have been coming down in recent weeks as production returned to where it was before Hurricane Katrina hit the Gulf Coast in late August.

Locally the high diesel prices are hitting businesses that use it to power construction equipment and buses. They've also resulted in skyrocketing interest in diesel made from restaurant oil.

John Orr, equipment superintendent for RCI Construction Group's Pacific division, said the cost of filling up his diesel-powered truck's 40-gallon tank rose from $80 to $125, and he fills up three times a week.

"It's overwhelming," said Orr. The company's projects in Hawai'i include building the north-south road in 'Ewa, military communities near Honolulu International Airport and a sewage treatment plant on Sand Island. Orr buys in bulk, sometimes a 1,000 or 1,500 gallons at a time.

"It's adding tens of thousands of dollars to the jobs we currently have," he said. "You try to recover that from who you're doing a job for and of course they don't want to pay the extra money. So it's a loss to us."

At Roberts Hawai'i, the state's largest tour bus company, fuel costs have risen 32 percent since the start of the year, said David Goya, company chief financial officer.

Some of the increased diesel costs were offset by a 2.8 percent rate increase approved by the Public Utilities Commission that went into effect Oct. 1 for all bus companies.

"We're not able to pass on all those costs to our customers," Goya said. "It definitely has a bottom-line impact as it does to anyone who's running vehicles."

Like RCI Construction, Roberts has taken to making sure its equipment is running in top condition, making sure its drivers take the most efficient routes and minimizing the moving around of equipment. Roberts also is reminding drivers not to idle buses excessively.

The jump in diesel prices have the phones ringing at Maui-based Pacific Biodiesel Inc., which will process about a million gallons of used restaurant oil into diesel this year. It sells the fuel for $2.84 a gallon on Maui and $2.91 on O'ahu.

"It's been phenomenal," said Kelly T. King, Pacific Biodiesel marketing and communications director. The company hasn't been able to keep up with demand and has created a waiting list of those wanting the fuel.

King said the company wouldn't be able to come close to fulfilling the state's diesel demand even if it were able to get another 1 million gallons of used restaurant oil that may be available annually.

To increase the supply of vegetable oil, King is working with legislators to propose a demonstration project to grow seeds that can be processed for the fuel.

Aikane Sport Fishing's Rivera said he hopes the price of diesel comes down because he doesn't want to hike his rates again.

"I don't want to raise it so high that all of a sudden I don't get any more customers," he said.

Reach Greg Wiles at gwiles@honoluluadvertiser.com.