The U.S. Department of Transportation more than doubled civil penalties for fuel economy violations last year after Congress ordered agencies to adjust their fines for inflation.
The new rule, which was set to take effect in July, would require automakers to pay $14 for every tenth of a mile per gallon of fuel a vehicle consumes over its minimum. Since the mid-1970s, automakers have paid $5.50 for every tenth of a mile per gallon.
Automakers objected, saying it would cost them $1 billion per year. The federal government delayed the rule in July.
Vermont, Maryland and Pennsylvania filed suit as well.