You're expecting a lot from an oil if you think it's going to catch up with a dirty engine. If you want to do it on the cheap, get a big bottle of MMO, drain off 10% of your oil and top off with MMO at 1k before the next oil change. Then about 100 miles before the oil change drain 10% again and top off. Then do your normal oil change and at 1k before the next change do it again if you need it, and keep doing it as long as you need to. While you're doing this dump a big dose in the gas tank to. Crude but cheap.