A gun cleaner is a solvent that breaks up the residue left behind when a round is fired from a firearm. It can be in liquid or aerosol form. When choosing a gun cleaner, it is important to select one that matches the method used for lubricating the firearm. For example, if grease was used for lubrication then grease-based cleaners should be used to clean the firearm because other types of cleaners would break down the grease and cause malfunctioning of the firearm. For routine cleaning, water-based cleaners are preferred over oil-based cleaners because they do not attract dust or dirt like oil does.