What should I use Zmax, MotorKote, other

I have a 1994 Honda Civic CX 4 cylinder with 165,000 miles. It is currently running on 3 cylinders, and smokes. I think that the piston rings may need to be replaced, but I'd rather not spend so much money. Is there anything out there that would help my car, and possibly get all 4 cylinders running once again? The Zmax infomercial claims to condition piston rings to help them seal better, but I am very skeptic about all of these claims. I would greatly appreciate anyones advice. Thank you!