You can also (and people do) put ATF, MMO and STP in the crankcase, but who would??
Now if the Chevron Techron container said one add to the crankcase, that would be something I would want to know more about.
I added 6 ounces of Gumout Multi-System tune up to a 2002 Jeep Wrangler 4.0 that had a good amount of sludge under the valve cover.
I added the 6 ounces to the oil and started the engine. The engine instantly exploded and killed everyone and everything in a 6 mile radius! I am typing this as a ghost and coming to haunt you next!!!
No. Actually I added the 6 ounces of Gumout and drove normally for the last 1,000 miles of the oil change interval. Nothing bad happened, no check engine lights, not even any weird sounds occurred. If anything the little bit of valve train noise this engine has seemed to go away. During the oil change, the oil was very black as usual and nothing else strange happened. Looking under the valve cover with my inspection camera after the oil change, the valve train looked a lot better than before. The thick black sludge that was sitting in the corners and low spots was almost completely gone. Once the engine was refilled with oil and started, the valve train noise did not come back and has not come back yet.
I would say The Gumout Multi-system tune did help clean up the engine more than just a normal oil change alone. I can't report anything bad happening and the Jeep is still running well.
These were my findings and I am happy with the results. Do what you want to do and as always, Your Mileage May Vary.