I used to be very interested in every oil supplement that came along, although I tried only a few. And I did use Tufoil for a few years.
Today I mostly stay with Auto-RX (cleanings about every 25,000 miles and then maintenance doses), fuel system cleaner (Techron or Regane in clear bottle) every 3000 miles or so, Stal-Bil in lawn mower engine gas, and rarely Marvel Mystery Oil, Bar's Leaks, and maybe I would try Lubegard Engine Flush if I could find it. I have to say that I went a long time before I started up maintenance doses of Auto-RX again. And I have occasionally gone a long time before using fuel system cleaner.
In fact I try to keep the gas fresh enough in my gas container so that I don't even have to use Sta-Bil, and aside from Auto-RX and occasional fuel system cleaner I have pretty much given up on additives and supplements. I even went a long time before I started up Auto-RX maintenance doses again.
Today I mainly try to make sure all necessary maintenance is done and quality oil and air filters, etc., are used. I am not much of an additive guy anymore.