In addition to having stricter fuel economy requirements, the Senate bill contains three major differences. The first is the maximum fuel economy of the trade-in vehicles, which is 17 miles a gallon. The second is there are three voucher amounts ($2,500 to buy a new car that gets at least seven miles a gallon more, $3,500 for 10 m.p.g. more and $4,500 for 13 m.p.g. more). Finally, the Senate bill also offers a provision for buying a used car.