Today, GM's Active Fuel Management system works great— you can get 29 mpg from a car that runs 0-60 in under four seconds, and you never even notice when the system turns your V8 into a four-banger. However, GM's first attempt to sell an engine with cylinder deactivation— the 368-cubic-inch V8-6-4 engine, available starting in 1981 Cadillac models— turned into a horrible disaster for The General (things got even worse for Cadillac soon after that).
The V8-6-4 system theoretically worked via solenoid deactivation of the rocker arms on two or four of the engine's cylinders, but it never worked so well in the real world. Coupled with the Oldsmobile Diesel 350 fiasco of the same period, the V8-6-4 gave GM a black eye that took a long time fading away.
Thanks to certain global events, fuel prices had gone crazy in the early 1980s, and the idea of making Cadillacs gulp a bit less gas seemed like a fine idea. This ad shows sort of an idealized version of the life of a V8-6-4 owner.
