I've been collecting saws for many years and i find that if a saw sits on a shelf for a long time the oil will get gummy and eventually dry-out and some dissassembly and cleaning will need to be performed.
The only thing so far that i use without problems is transmission oil...it is not petroleum based and it does leave a permanent coating on all internal parts.
It is not harmful to any seals and on the contrary it prevents shrinkage and cracks and the seals stays souple.
As for restarting a saw that has been stored....i simply pour gaz mix in the muffler and crank the engine slowly then turn it around to empty the base and it usually start pretty easy.(use your judgment and dont pour a gallon of tranny fluid to make an hydrostatic lock-up).....otherwise your in big trouble..........
This process needs to be perform at the muffler since many saws have reeds that will not allow oil to enter the base.......piston ported saws on the other hand will allow oil to be poured at the carb.
Alain,