Again, I would recommend that you NOT add seafoam to your engine oil. If you have been using a quality oil, and changing it regularly, there should be NO sludge, etc (zero, nadda, absolutely nothing!). If there is, then there is something wrong with you engine oil or maintenance schedule.
Small amounts of "varnish" type deposits can and will accumulate on hot areas, but these aren't coming off will a little treat of extra detergent, they are in fact "baked on". Again, a quality oil will minimize this.