My dad was the KING of "Liquid Tune Up" type products. He was tossing additives into brand new cars that had no miles on them! Long story short, my mom's Ford Econoline conversion van died an untimely death after overheating and blowing head gaskets with only 40k miles on it. This was a direct result of "preventative maintenance" by adding Bars Leaks into the coolant so it wouldn't "develop a leak", Gobs of liquid engine re-build went into every car he ever owned and he couldn't resist a weekly can of "STP Oil Treatment" (Which basically turned his motor oil into superheated chewing gum). I found a Ford Bronco II on Craigslist for $200.00 with a blown head gasket. It still ran when I got it, but not very well! I dragged it home and cracked open the heads to find this: Notice the COMPLETELY PLUGGED water jacket passages in the head gasket below: I love to buy cars like this. I get 'em cheap, get 'em runnin' cheap and sell 'em! All of this was caused from a $10.00 bottle of stop leak. Think about that next time you think about using it! LOL!