Consumers less willing to buy Hyundai

On Nov. 2, Hyundai immediately apologised and agreed to compensate owners for the additional fuel costs, but Visnic said the cost could increase given lawsuits over against the false mileage claims.

"Also, there could be a cost in future business as this development may have a direct impact on Hyundai's credibility with some U.S. buyers," Visnic said.

Moody's Investors Service previously estimated that the automakers' compensation plan would cost them $100 million a year until the cars are scrapped but has not estimated potential legal costs.