The FI systems on the new cars are quite efficient and do get good mileage. But, the newer cars are also lighter, more aerodynamic, and the 6 and 8 speed double overdrive automatic transmissions make a huge difference. If my boxy 70 Dart with a 318 2 barrel, 3 speed auto transmission (and no lock up convertor) and a 3.23 rear gear can get 19, and a 65 Dart with a slant 6 and a 2.76 gear can get 25 mpg, who needs a $2000 FI system.