Can methylated spirits or other alcoholic based fuels be purchased for camping from a camping shop in Israel if they were owned over Pesach and likely not sold?
It is permitted to buy such fuels, even if they were not sold. Even for pure alcohol, it is very hard to verify the origins, and therefore there is always a matter of doubt as to whether there is a chametz issue or not. In addition, if other chemical ingredients are added, in order to create the required finished product, the prohibition will likewise not apply. Because of the doubts involved, there is no need for stringency concerning the rabbinic prohibition of chametz after Pesach.