.
Big high compression engines of the late ‘60s got really excellent gas milage.
Chrysler 426 HEMI displaced 426 cubic inches and produced 425 horsepower at 5,000 rpm and 490 foot-pounds of torque at 4,000 rpm. It had 10.28:1 compression and required the use of premium fuel. It used two four-barrel carburetors for air induction and cast iron exhaust manifolds. Fuel economy for the 426 HEMI was factory rated at approximately six miles per gallon.