We can guarantee your grill will be cleaner than when we arrived. Unfortunately, we cannot guarantee how clean your grill will be when we get done. There are so many variables that can affect how clean your grill can get like the age of your grill, how dirty it is, the grade of stainless steel, what type of grilling you do. While we can generally get most of the grease and build-up off what we can’t remove is the rust, deep metal burns and age. We simply cannot remove the rust from the metal. If you have a Weber grill the cast aluminum fire box is extremely difficult to clean and will remain black and stained forever.