I think that motor oils are designed to operate at the extremely hot temperatures it encounters inside of an engine. It can maintain its viscoisity under high heat and friction. It absorbs pressure between moving parts. Absorbs and carries away heat. It has detergents to to aid in keeping the moving metal parts clean. It prevents rust very well also. I do know that convential motor oil will will break down alot sooner than a synthetic. Synthetics usually do everything conventials do, but better.
There is absolutly no reason I can find as to why you cant use motor oil to lubricate your weapons internals and moving parts. Even a light coat in the exterior metals to prevent rust. However, I would not use it to in the chamber or barrell. Motor oil has enough "thickness" to possibly alter the inside deminsions of the chamber. This is just my assumption. I wouldnt use it in the barrell because motor oil flameable, and hard to extinguish. It would be good in a barrell for long term storage of the weapon, but mopping the bore would be critical before firing. Excessive pressures in the gun may result if not.
Ther is no reason you cant use it, other than the smell. Synthetic usually smells a bit better than convential. Id reccomend something in a 10w as it is a lighter colored oil with less odor usually. And its a bit "thinner" then the 15, 30, 40 and 90wt stuff.
Just my opinions.
I just use the military CLP from the armory. It smells great and I put it on my pancakes in the morning.
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