Congress OKs $2B refill of 'cash for clunkers'. Under the program, passenger car owners are eligible for a voucher worth $3,500 if they trade in a vehicle getting 18 miles per gallon or less for a new car getting at least 22 mpg. Vouchers of $4,500 are available for owners who trade in a passenger car getting 18 mpg or less for a model that gets at least 28 mpg