Although multiple experts said that we could in theory cook without any oil or butter, we found this to be difficult in practice. Even on our top picks, a dribble of oil would probably have resulted in an easier fried-egg flip, and buttering the bottoms of the pans prior to baking would have helped our cornbread come out in a solid loaf. That said, every expert warned us away from using cooking spray. “Never use cooking spray because it will result in a buildup that causes your food to cook unevenly,” Green told us. Too much cooking spray residue can also make nonstick pans sticky, which kind of defeats the whole purpose — and both All-Clad pans came with documents stating that using cooking spray on the pans would void the warranty.