I have been using USGI surplus CLP(cleaner,lubricant,preservative) for 20 years and it still is current issue. The commerical equilivent is
www.break-free.com/After using it to clean my firearms, I give the inside a coating of it to lubricate the moving parts,and also give the outside a coat of it to preserve/protect it from corrosion(rust).
CLP has mircoscopic teflon particles in it that get into the pores of the metal and is a very good lubricant. A added benifit of the teflon in the pores of the metal is fouling doesn't stick as hard to the metal.
You know how hard the carbon is to get off the gas piston. It requires lots of scrubbing with a brass or steel brissel brush to remove. Lubed with CLP before firing all that is required to remove the carbon is spaying it with CLP,letting it soak for 10 minuites. Then using a tooth brush with plastic brissels and it doesn't take that much scrubbing to remove the carbon.
Try it one time and you won't use anything else.