How do you unfreeze a mower engine?

To unfreeze a mower engine, start by removing the spark plug to relieve compression. Then, apply penetrating oil into the spark plug hole and let it sit for several hours to lubricate the cylinder. Afterward, gently try to turn the engine's crankshaft using a wrench; if it doesn't budge, repeat the oil application. Once the engine turns freely, replace the spark plug, and you can then attempt to start the mower.