Old time super modified driver Willie Stutzman had a car that was sponsor by Du More water softer company. I may be off on the spelling. The logo was goes in hard comes out soft.
Back in the 80's there was a Super Vee car sponsored by a European prophylactic company and it had a brightly colored unrolled one painted on the side of the car. I was at Milwaukee with my 9 year old son and we had Paddock passes. All around the car were scantly clothed models and my son looks at them then the car and asks what is that on the car!
This might be a little O.T. but several years back in ca. a racer had on the rear door of his trailer " WARNING!! behind this door is a disease for which there is no known cure"