A federal appeals court yesterday unanimously rejected a consumer group's attempt to force consideration of stiffer fuel mileage standards for cars built after 1985.

The U.S. Circuit Court of Appeals here dismissed a suit filed by the Center for Auto Safety after the National Highway Traffic Safety Administration dropped its plan to begin looking into fuel economy for cars in the 1985 to 1995 model years.

However, two of the three judges said that the suit was premature and that the group could try again next year.

Specific fuel-mileage standards for new cars and light trucks have been set by law or regulation from 1978 through 1985. But Congress left it up to the NHTSA to decide whether cars built after that should beat or merely meet an average fuel standard of 27.5 miles per gallon.

In the closing days of the Carter administration, the safety board announced that it would begin gathering public comments on future mileage standards.

However, the plans were dropped after the Reagan White House issued a presidential directive in April, 1981, to aid the ailing auto industry.

The consumer group, which favors stiffer mileage standards for cars built after 1985, eventually filed suit challenging the reversal.