> Vehicles from the early 70s often had similar gas mileage to smaller lighter vehicles from the late 90s-early 2000s but the newer cars had much better emissio

> Vehicles from the early 70s often had similar gas mileage to smaller lighter vehicles from the late 90s-early 2000s but the newer cars had much better emissions. Source? Electronic fuel injection with closed-loop fuel/air control wasn't a mature technology in the 1970s, and open-loop fuel injection (not to mention carburetors) combined with 3- and 4-speed transmissions are inherently less efficient then closed-loop with 4, 5 and 6-speed transmissions.