suck. Period. Here is why. They last for 30-50k miles as they advertise depending on the quality of the product. Then that stuff starts to flake off in microscopic particles that score up the walls of your cylinders, rod bearings & main bearings. If you add the stuff once.. you had best keep adding it cause if you dont.. it will eventually eat your engine from the inside out. There is no magic fluid in a bottle that will mystically restore your engine or adequately provide restoration to your engine if its been subjected to serious neglect. There is no replacement for maintenance
Now.. some of the better products out there will help keep your engine younger and reduce friction and wear excellently.. but you still have to change the oil and replace the oil filter when your supposed to. I would still have to recommend avoiding using things that "Bond" to your engine surfaces. No bond is permanent and eventually.. something is going to be floating around that you dont want in there.Tunes67