Heating oil prices are up this year, but oil use in Maine is going down.

That contradiction — a price increase despite a sharp drop in demand and a relatively stable supply — suggests that trying to predict what Mainers will be paying for heating oil in a few weeks, let alone a few months, is foolhardy, said Jamie Py, president of the Maine Energy Marketers Association, which represents many Maine oil dealers.

“Normal supply and demand … has now become the supply and demand of financial instruments,” Py said, with the market for oil now dictated mostly by commodity speculators.

Oil use in Maine has plummeted in the last five years — about 70 percent of the state’s homes rely on oil heat as opposed to 80 percent in 2007, according to the latest U.S. Census.

Homeowners have replaced older, less efficient burners, insulated their homes better, supplemented their oil furnaces with wood- or gas-fed stoves, and switched to other fuels.

The statewide average price is now at $3.68 a gallon, according to the Governor’s Energy Office. That’s up nine cents from the average in August and 18 cents above the price at this point of the season in 2011.

Meanwhile, oil supplies have remained relatively stable over the past few years.

Py said it used to be simpler to predict prices, usually by looking at supplies and long-range weather forecasts — which, by the way, call for a colder and snowier winter this year than last year.

In the last few weeks, the oil market has worked in consumers’ favor.

Unease over the direction of the U.S., European and Chinese economies has led speculators to push the price of crude oil down about $7 a barrel since mid-August. On Friday, the price dipped below $90 a barrel, with traders anticipating that slower economic growth will reduce demand for oil. Prices were much higher earlier this year, peaking at nearly $110 a barrel in February.

John Peters, vice president of Downeast Energy, agrees that pricing has grown more complicated.

He said factors now include the state of various economies around the world, the value of the dollar and the status of political flash points, such as how Iran might react to tighter economic sanctions and the plummeting value of its currency.

“It’s all of those things, on any given day, thrown into a pot,” he said. “If it were a function of supply and demand,” oil would cost far less.

That volatility isn’t causing a stampede to plans that guarantee or cap prices, Peters said.

His company has seen slightly more interest in fixed-price plans, in which homeowners buy an entire season’s anticipated oil supply, upfront, at a set per-gallon price.

That satisfies customers who want to control their costs, Peters said, knowing that their household budgets for heating oil won’t be affected if prices jump 30 or 40 cents a gallon. They’re not likely to be upset if they end up paying a few pennies a gallon more than the price they might find by shopping around when they need oil, he said.