They are recoil operated gun and as such do not get dirty like the gas loaders. If you feel the need to oil and clean, keep the exterior lightly oiled to protect the bluing, after shooting, especially in the rain etc. As for cleaning and oiling the internals, the receiver portion can be cleaned and lightly oiled on any action surfaces. IE where the bolt is moving back and forth, triggers parts etc. DO NOT OIL under the fore arm. These gun use friction rings on the mag tube to slow the action, as you will find out the barrel on the auto-5 moves backwards when fired the inertia from the shot throws barrel back with opens the gun and if another shell is present, the spring sends the bolt forwards again.
long story short oil and friction rings don't mix