Quote from imq707s on 03/29/10 at 21:44:13:I have a little bottle with some Mobil-1 15w-50 oil (I use it in my sportbike). It works great on the rails of my 1911, and on my AR-15. It's a little thicker than your standard gun oil...but it seems to last longer, and not try out as fast. I have been using it for a while, and so far it seems to be working great.
I am amazed this topic is still going strong! I used the formula that was provided by CJ : 2 parts 15/50 Mobil 1 and 1 part Mobil 1 transmission fluid. I use it on all my weapons now and had smother operations on them. I also use the M1 grease when I need a point that needs it. See Cj's post on this thread.

As far as protection on the outside parts the synthetic will cling better to metal and stay longer.