Starting in April, the state mandated that most gasoline sold in Hawai'i contain 10 percent ethanol. The goal was to reduce the state's dependence on imported oil, but oil imports are still rising.

Oil companies say the 19 percent increase in imports through September is caused in part by the need to produce jet fuel and fuel oil to generate electricity.

Through October, consumption of gasoline (with ethanol) is up 3.3 percent, compared with the same period last year. The increase was expected because ethanol-blended gasoline contains less energy than pure gasoline. That means drivers have to use up to 3 percent more fuel to cover the same distance.

Consumption of pure gasoline has fallen about 7 percent, with ethanol making up the difference. The ethanol is imported because there are no local ethanol factories. There were 991,000 barrels of ethanol imported into Hawai'i through September from countries such as El Salvador.

Reach Sean Hao at shao@honoluluadvertiser.com.