Back when I was a puppy, the old dogs of that time advised you could add a quart of kerosene into you
oil to clean sludge out. I did that several times with junk yard engines and used cars I picked up cheaply. I would let them idle about 15 minutes and then change the
oil.
One particularly sludged up 283, I put in a Vega (I was building a 327 to put in it later), I added Kerosene and decided to leave it in to soak and clean until the build was done. I just started it to move it once in a while. After I finished the car, I forgot about the Kerosene and drove it around town for a day - maybe 50 miles. I destroyed the rear end on the way home. When it let loose, the engine likely hit 10K on a free rev (pegged an 8K tach). The engine seemed fine after that. I sold the engine to a friend who sold it to someone else who planned to rebuild it. The guy claimed all 8 rod bearings were spun. I always doubted it, as it ran just fine when I pulled it, but I will never know for sure. Bottom line, if you do try this trick. Let it idle a bit and then change the
oil immediately. Don't repeat my stupid stunt.
PS
The guy did say the engine was clean as a new one. I had changed the intake, and it was hideously covered in sludge, so the Kerosene does clean them up. Wonder where it all went? Through the bearings?