I use this stuff my dad gave me called wire rope and chain lube. It's a tacky oil which comes in a spray can, I love it. He has this crap by the case so I always grab a couple cans whenever I'm over there. I spray this on the underside of my bed, inside fender wells, and also into every hole there is in my frame. Good thing for me is that this stuff doesn't drip off the truck into my white concrete driveway. I once saw a can of similar stuff at Home Depot, but I can't seem to find it anymore.

83 4x4, 3" Lift, 33" Buckshot Mudders