Hi 39,
What happens is that the vehicle is parked with well oiled valve stems and well oiled valve guides and the engine is allowed to just sit unattended.
Over quite a bit of time, the volatiles in the thick oil evaporate & it leave a dense sticky petroleum residue on valve stem surfaces and valve guide surfaces.
If one wants only a 24 hour soaking, this sticky residue can be dissolved with a thin liquid with more of a cutting action like thinner kerosene or diesel.
Liquid Wrench I found works far faster, but is more expensive ..... thicker Marvel Mystery Oil may work, I just never tried it.
Learned long time ago to try what once worked successfully ...... time is of the essence, and life is too short to try to experiment with everything in life that may not work. LOL