I recall an episode of Chasing Classic Cars and Wayne's old-time mechanic, Roger used MM to unfreeze a locked up engine in a car they had acquired. Took him several days using MM down the cylinders and gently rocking the car while in gear, to eventually free the motor. Apparently that's been his go-to method for some time. Regardless if you like the show or not, Roger's da-man and deserves major creds, especially considering he's in his 80's.