Watch in a jar of lighter fluid.

My hubby has a self winding watch. A weight goes around inside it that winds up the mechanism. It has stopped working when he takes it off at night. He has had it for years and like all his other stuff he has an emotional attachment to it. Remember my picture of him repairing a leather belt that he has worn every day for 39 years. Anyway we went to a watch repaired who said, as we suspected,that the oil has become a bit thick inside the watch and it needed cleaning. Cost 200 pounds. I was shocked and researched on the internet what to do to make it go itself.
The suggestion was to take off the back and suspended the watch above some lighter fluid in a sealed jar. The volatility of the fluid means molecules move around inside the jar and combine with the oil in the watch thinning it. I asked my chemist friend and she said that should work. Also people on line have commented that it worked for them. Fingers crossed. There's nothing to lose.