Automotive products will contain additives you don't want and lack ones you do want. In particular motor oil will not inhibit rust as well as a good gun oil.

Not an Earth shaking difference, wheel grease is certainly better than no grease, but I still hold to the idea that for the purpose lubricants are a little better.

As for the grease cushioning the hinge pin hook interface, it bothers me a little that working the action a few times tends to wipe the grease away from the area where it is most needed. No easy answer for that one I guess, except that I regrease before each shooting session. (Clean away the previous grease, dust or no dust, so you don't end up over lubed.)