AUGUSTA – Maine motorists have one last weekend to gas up before fuel prices go up.

On Tuesday, Maine gasoline and diesel fuel will be a few cents more expensive as the tax on each rises due to a year-old state law that for the first time will index Maine’s motor fuel taxes to inflation.

A major auto travelers’ group grudgingly accepts the 2.6-cent-per-gallon gas tax hike, while a truckers’ organization says the 2.7 cent rise in the diesel levy hits at a bad time.

The actual increases that motorists see at the pump will likely be a few tenths of a cent higher than the added taxes.

Retailers typically mark their pump prices to end with .9 cent. With gas taxes going up to 24.6 cents and diesel to 25.7 cents per gallon, they’re not likely to start charging prices ending with .5 or .7 cent, said Matt McKenzie of AAA’s Portland office.

More likely, retailers will ratchet their prices up to the next .9 cent per gallon.

“We’ll see an increase of 3 cents per gallon,” McKenzie predicted.

The statewide average price as of Thursday was $1.45.8, well over the $1.37.1 price of a year ago, according to the AAA. Current averages vary across the state, with the Lewiston-Auburn area recording a low, $1.40.6.

The AAA has yet to hear complaints from motorists, McKenzie said. The travel organization itself scrutinized the increased levy and weighed it against the alternative – seeing Maine’s highway and bridge maintenance and improvement program suffer, he said.

“The best alternative here was to raise the tax,” McKenzie said.

The Maine Motor Transport Association acknowledged the state needs the money for transportation expenses, but said truckers have had a tough year with their fuel prices rising 15 percent to 20 percent over 12 months.

“It certainly comes at a tough time for everybody,” said Dale Hanington, president of the truckers organization.

Maine gasoline retainers located near the border with New Hampshire will be put at a greater competitive disadvantage because the Granite State’s gas tax – 18 cents a gallon – is relatively cheap, said Jamie Py, president of the Maine Oil Dealers Association.

For retailers competing head to head, a 7-cent-per-gallon difference is “huge,” he said.

The price jump also puts gasoline retailers in an awkward spot because it will prompt questions and complaints from their customers, said Jim McGregor, vice president of the Maine Merchants Association.

Anticipating questions from consumers, convenience store owners and other retailers asked the oil dealers group for stickers they can put on their pumps explaining why gas taxes are going up, said MODA’s Py, who had 1,000 of the stickers printed.

McGregor said customers for the most part will not remember it was a previous Legislature that authorized what he denounced as “a stealth tax” by “automatic pilot.”

The law that authorizes indexing requires a legislative vote on whether to repeal any fuel tax increase before it can take effect.

Without taking a stand on whether the added fuel tax is justified, McGregor supported a bill this year to block the planned increase, saying that each new tax is fair game for legislative debate.

The same law that’s nudging Maine’s gasoline tax up this summer could hike it by another half-cent in a year.