A federal judge has ordered Exxon Mobil Corp. (XOM) to pay damages to more than 10,000 gas station owners who were overcharged for their gasoline for more than a decade, a ruling that could cost the company $1.3 billion, an attorney for the plaintiffs said on Friday.

An Exxon spokeswoman said the company would appeal.

Under the order handed down in Miami by Judge Alan Gold on Wednesday, Exxon would have to pay the class members damages of 1.3 cents a gallon for every gallon of gasoline they bought from the company during the 1983-1994 period, attorney Mark Dikeman said.

In some cases the potential recoveries are more than $1 million, he added.

The suit was filed in May 1991, and Exxon's liabilities were established at trial in 2001, but payments were delayed while Exxon appealed. Those efforts were ultimately unsuccessful, and with accrued interest Exxon now potentially owes the class members $1.3 billion.

Exxon spokeswoman Prem Nair said the company took a charge of $550 million against 2004 earnings to account for potential payments of damages to dealers and station owners but said the company disagreed with Judge Gold's latest ruling.

"We were seeking clarification on a number of legal issues that we thought were not resolved by the appeals process," she said. "Unless each dealer is required to prove damages some dealers who were not damaged will receive money and we think that's not right."

Shares in Exxon were off 47 cents at $54.36 on the New York Stock Exchange (search).