Internal engine cleaners/additives

Generally speaking, I don't like any oil additive at all. It changes the viscosity and chemical makeup. If you run 10x30 and add in an additive, it's not 10w30 anymore. You'd have to send it in and get it analyzed. I do like and recommend sea foam, but that's a little different. It's not meant to be permanent. You run it for a given period, then dump it out on the next oil change. Plus, it's such a light viscosity, it's not changing much, if anything. The bottom line though has already been said. Run the correct oil to start with and keep it changed regularly. That's the only right answer.