if you want to clean anything out, go find and order AutoRX... it is the best "engine flush" there is as it is gentle and takes LOTS OF TIME to clear out whatever is in there. Since it is slow action, it will not quickly remove globs of sludge that will stuff up an engine. This stuff is often discussed on the BITOG forum and many will vouch for its safe effectiveness

You must use cheap regular oil though. No synthetics, no semi-synthetics, and no fancy extras in some dino oils. Otherwise it will not be effective