I was not happy with a 1.5l Mitsubishi 12V engine the wrecker sold me - made quite a clattering noise, and the inside looked heavily varnished, even though the engine was powerful enough, and started right away...so...I drained 2 quarts of oil, and replaced with 2 quarts of kerosene, ran for 10 minutes with my foot very lightly on the throttle (in neutral, in the driveway). when i took my foot off the throttle, you could tell the engine was starved for lubrication, because the idle speed was dropping below normal.
After 10 minutes I drained out the mess, which was very black, and then replaced with 4 qt. of ATF, run for another 10 minutes, drain, again very very black, then fill with 4 qt of cheapo oil, run for 10 minutes, drain, this time oil comes out clean, and now replace filter and fill with 5w30 SM engine oil.
I would never do this again.
The engine ran exactly the same afterwards. I noticed it was using 1/2 qt oil per 1000 miles, but I don't know if that was something new, due to the "cleaning", or if that was the original condition. I might be a little of both, but this Mitsubishi is known to be a good little engine, and should not be using oil at the age that was claimed (60,000 miles). I suspect this engine was abused before it ended up in the scrap yard.
However, if you do want to do the full Monty, then you drain the entire crank case, replace with kerosene, run for 10 minutes, and then fill entire engine with kerosene, right to the top, and let sit overnight. In a.m. remove spark plugs, and crank over the engine several times. make sure to have the fire department on stand by when attempting this, because fuel will come rocketing out the engine as it is being turned over. then drain the whole works, replace with oil and new filter, and a week later drain oil again, and replace with fresh. Engine will now be "clean".
p.s. due to a collision, one of my Mitsubishi Colt had to be written off, so the "cleaned" engine ended up going to the scrap yard, and replaced with an engine with 30,000 miles on the clock, and I know the owner, engine not abused, does not use oil, and will not be punished with a "cleaning".