I'd only use non-ethanol fuel in it. The alcohol that is in the blended fuels absolutely kills carbs over time. Since you don't know what kind of junk you have in the fuel tank, be religious about changing fuel filters (I had one go bad - it broke apart within the housing and let a bunch of junk get to the carb, plugging it). I would also run SeaFoam as a fuel system cleaner and some sort of preservative, such as Marine grade Stabil or the Star Tron stuff. You may think it's all advertising hype, but I've had poorly running motors clear up with a dose of SeaFoam.