I went from an '03 Silverado C2500HD 6.0L gas to a '22 Colorado ZR2 3.6L gas. I needed a new truck and needed something to fit in my garage, so I downsized. I have no idea what kind of mileage the Ram Rebel gets but I have to say, my ZR2 is no sissy when it comes to chugging gas. If your reason for considering downsizing is mileage, please make sure you will get what you are expecting.