3in1 is very light and apparently doesnt leave much or any residue, and if planet says thats what you should use then that's what i will supply.
It makes sense to me that a light oil should be best for a high speed pneumatic rammer, dow33 seems too thick to me, maybe planet fealt the pros outweighed the cons? you are afterall supposed to clean and lube the rammer and rammer housing after every days play.