I had a similar experience ... I tried a half tank of if and the carb/saw somehow didn't seem to respond right during adjustment. It had an unreal un-natural odor to it (almost didn't smell like gas -- too explosive smelling) and you could smell it from 15-feet away, as soon as you took the cap off the gas can. It smelt like it would melt anything it touched. I put a few ounces of it (mixed 32:1) in a saucer to clean some carb parts, and returned in about 10 minutes, and the saucer was empty except for a small residue of oil and gum. The rest had evaporated, on a 40° day. My saw misbehaved after half a tank, and I didn't want it for cleanup, so I took two gallons of it to the disposal depot at the dump, and went back to Amoco Ultimate, which a tanker driver told me is supposed to be straight distillate as it comes from the refinery, without any additives dumped in at the tank farm to "make" octane rating.