I used the Slick50 products in my 73 W200. Fuel treatment does clean system all the way to the tailpipe. clean as a whistle.
The oil additive sticks and stays on an surface it touched, very slick. I let the oil drain for 2 days before I replaced the pan gasket after using Slick50. The crank was still loaded and slick with it. I couldn't hold on to the scraper after touching the crank.