Like most other things, a generalized, "broad brush" statement is usually not 100% correct. True, some petroleum lubes will tend to foul. T/C Maxi-Lube, and CVA Grease Patch, come to mind. However, I use Hoppes #9 Plus Black Powder Solvent And Patch Lube, and it is great stuff. Definately does not promote fouling. Funny thing is, one of the ingrediants on the label is Kerosene. Last I knew, kerosene is a petroleum product. I think that the "All Natural" approach to lubes and cleaning, is a marketing ploy by the makers of these products. I also use Clenzoil, as a rust, and corrosion inhibiter, in the barrels of my ML's after cleaning. This too has petro products in it. True, I wipe the barrel to remove any trace of oil before initial shot. I have used the "All Natural" products, and see no difference in fouling than what I now use.