MF these motors are tough and can take incredible abuse. I come across a lot of these and only occasionally find one russted up and they have obviously been left in the open for years. The oil in the fuel obviously helps but I wouldn't get too fussed about the fuel evaporating and leaving the oil, only helps protect it. I have pulled primer caps off and the bowl is half full of oil. Just give them a quick start every 6 months , run for a few mins and all will be good and don't use ethanol fuel, to be avoided at all costs as AVB has reminded us
