Like the Cadillac Northstar? The cylinder deactivtion (just deactivating the injectors, not the valves) was one of the big features when it was introduced. Supposed to allow you to run for some time with NO coolant!
How many gears does that excursion have? I know the automakers have been putting more than four gears in the automatics thesedays. That could explain the good mileage and acceleration.