Consumer preferences drove controversial changes that will make the Subaru Outback sedan sold in the United States a 'truck' under federal fuel economy rules, a Reuters report said.

The modifications are meant to give the wagon version of the Outback a more rugged look as carmakers flood the market with competing models, all aimed at buyers looking for sport utility vehicles that ride and handle like cars, the report said, noting that environmentalists charge that the changes exploit a fuel economy loophole.

"It's becoming increasingly difficult to put all these cars into nice categories," said Subaru's US executive vice president Fred Adcock reportedly said, adding: "Things just don't fit like they used to."

Reuters said that Fuji Heavy Industries unit Subaru launched the Outback in 1995 as a variation of its Legacy sedan and wagon fitted with plastic cladding to give them a beefier look and the move proved so popular that the Outback models began to outsell the plain Legacy versions, accounting for 54,930 vehicles in the US last year, down from about 70,000 in 2001.

According to the report, those models were classified as cars by US government rules for fuel economy and emissions that require all of a manufacturer's cars to average at least 27.5 miles per gallon in the 2005 model year while trucks average at least 21 mpg.

Reuters said one definition of a truck is a vehicle with four-wheel-drive that can meet four of five technical requirements for off-roading and Subaru officials say the new Outback models meet that standard, thanks mostly to a 1.1 inch increase in ground clearance.

The report said that about 95% of Outbacks sold in the US are wagons, but the four-door sedan will also count as a truck, a decision that environmentalists called an attempt by Subaru to exploit a loophole in fuel economy regulations. Calling the Outback a truck will likely improve Subaru's car average, while leaving plenty of leeway in the truck standards to sell larger, less efficient SUVs, Reuters added.

However, Reuters noted, the Outback sedan won't be the first sedan to be called a truck by the US government - that distinction went to the American Motors Corp. Eagle, a 1980s model which, like Subaru's models, had four-wheel-drive and a high ride height.

Reuters said Volkswagen, Audi and Volvo also sell wagons in the US that are classified as cars in entry-level form but get branded as trucks when sold in a all-wheel-drive, higher-ride height version.

Subaru general manager of governmental affairs, Jim Murphy, told Reuters the change from car to truck was a consequence of other decisions to make the Outback wagons more closely resemble sport utility vehicles, and was not a goal for Subaru.

"If we had wanted to make it a truck, we would have made it much closer to the standards," Murphy reportedly said. "In today's world, there's no benefit."

Reuters said the new Outback will have about a 5% improvement in fuel economy over the current model and average about 27.5 mpg, despite an increase in horsepower.