Cadillac offered a feature on its V8 engine called the V8-6-4, but only on its 1981 model, as part of its efforts to meet new fuel economy standards. When the engine is running at light loads, it is logical to shut down unneeded cylinders for fuel efficiency. However, it was a huge technical challenge in those days as the computer technology at the time could not deactivate or reactivate the cylinders fast enough. This prompted many owners to have the system disabled by mechanics. Cylinder de-activations are a common feature on large-engine cars today.