Does it really have an effect?

Question

Whenever I do an oil change I spend an extra 12 bucks for this very viscus stuff that you put in with the oil that supposedly makes it run better and cleaner. Do these types of products actually work? Or am I just getting ripped off?

Answer 1

if it is a newer car with less than 50,000 miles your wasting your money. those products are usually for cars with miles on them because it helps to fill in some of the excess clearance in the engine that occurs with high miles.  

Answer 2

Any of those off the shelf fix in a can engine products aren't necessary. If they were the oil companies would put those products in their oil.

Also anything that would make the oil more viscous is harder for the engine to pump causing power loss. Also, engine bearings seat and clearance themselves for the viscosity of oil you use which is why stepping back from a higher viscosity oil to a lower one is generally not a great idea. The lower viscosity oil can't fill in the gap as well and bearing damage(major $$$) can happen. Just use oil and keep your faith in the ASE-SAE ratings for oil. They know more than all of us.