Any oil additive that contains solid particles is BAD for your engine. That means anything with teflon in it. It blocks up oil galleries, it plugs filters, and it INCREASES engine wear.
Restore is pretty tricky stuff. Long term the only bad effect your likely to get would be lead, copper, and silver coming out in your emmisions. Maybe some sparkplug or catalytic converter fouling.
Don't use ANYTHING that claims to stop oil leaks. It's total rubbish. Find, and fix the source of the leak!
Don't use oil additives in new cars. There is a reason that new car manufacturers don't recommend any additives. The ones you actually need are already contained in engine oil.
