When I was a young man, living in Detroit, in the 60's, we used to take some of the oil drained from the crankcase at oil change time, put it in a squirt can and squirt it through any access available in the doors, fenders, quarters, etc. I think that it worked fairly well because when I sold my '58 Plymouth Belvedere in '66, before leaving for basic training, it was still rust free. My father wouldn't let me park it in the driveway though. I imagine that the oil stains might still be on the street.