The reformer is distinct from the fuel cell--which generates the electricity for a fuel cell car--but is critical in allowing the cell to run indirectly on ordinary gasoline.

Mitchell estimated that a fuel-cell car with the Arthur D. Little reformer could offer between two to three times the gas mileage of a conventional, internal combustion engine car, which gets no more than 30 miles per gallon for city driving.

"I would expect that the first ones would be somewhere between 60 to 80 miles per gallon," he said.

Others, however, said they were skeptical of Arthur D. Little's announcement of its reformer technology.

"In my opinion, it's an old technology," said Dr. Hans Maru, executive vice president and chief operating officer of Energy Research Corporation, based in Danbury, Conn., adding that a fully functional reformer was "years away."

Several auto manufacturers have expressed interest in using the Arthur D. Little reformer in their cars, said Derby. "We're having discussions with Honda and Toyota, and also with Chrysler," he said.

Premium Price

Today's fuel cells can not compete on a price basis with mass-produced internal combustion engines. The usual indicator of measuring the cost-efficiency of an engine is the amount of money required to build one that puts out a kilowatt of power (about 1.3 horsepower).

On that scale, an internal combustion engine is about $50 per kilowatt. In comparison, a proton-exchange-membrane (PEM) fuel cell--the ideal fuel cell for vehicles--costs up to $10,000 per kilowatt, according to Maru.

In addition, scientists must still determine how to maximize the power output of a fuel cell engine.

"We have to ramp up the energy in terms of getting high enough output," Derby said. Arthur D. Little's test run in October produced a kilowatt of power--but the fuel cell will have to put out at least 50 kilowatts to power a car.

But fuel cell proponents see these figures as a challenge, not an obstacle, and argue that mass production will shave down the price of a fuel cell vehicle to competitive prices.

According to Arthur D. Little financial projections, "they shouldn't be more than a thousand or two thousand dollars more than your typical vehicles," Derby said.

Coming to a Dealership Near You

Experts disagree as to when the public might see cars run by fuel cell engines hit the market.