It's actually a disaster. Google GM AFM (Active Fuel Management) current Billion $ class action suit against GM for fatal engine damage. What is going on in these engines is negligent and borders on the criminal. It is all about C.A.F.E. and corporate accountants. The engineers warned them.
Cylinder shut down for modern GM V8's can be defeated with a Holley "Range Tech" device that plugs into the OBD port. If your engine is still running well do it NOW. My 2013 Sierra 5.3 with a Range Tech stays in V8 mode full time and will enjoy a long life running as it is supposed to.
Chrysler (MDS) and the Ford Coyote V8 as of 2021 (also disasters) require a "defeat Kit" that is a lot more expensive (cam/lifters/labor). A RAM Hemi with an aftermarket performance exhaust system in V4 mode sounds like a Honda with a fart can. Owners are removing and back to stock. Still an issue but not so annoying. MDS is also the a likely cause of the "Hemi Tick".
Even the HP C8 Corvettes have cylinder shut down. Ridiculous but it can be defeated in one drives in Sport Mode all the time. Otherwise.......... buy a Range Tech device from Holley. The best $250 you will ever spend.
Fuel mileage savings with cylinder deactivation are pretty much a myth.