An acquaintance in the chain saw business has had an increasing number of units which use pre-mix being returned after having self-destructed. The manufacturer’s research indicates that, possibly due to the effects of ethanol or another chemical, the oil is separating out within a few weeks and no amount of shaking will mix it again. His advice is to only use premium brand petrol and mix as required – easier and cheaper than an engine rebuild.
Possibly good advice for any two stroke user.