Sounds like a great buy....$300.....WOW! Might have used ethanol? No matter what I preach, it seems about 1/2 of my customers are ignorant to the damage that ethanol will cause to rubber, certain plastics, as well as simple fuel degradation resulting in octane fluctuation and ultimately damaging corrosive deposits. A problem with ethanol that it actually "invites moisture". This makes it a problem in marine environments as well as aviation, "where it is actually illegal to use". If your plane goes down the FAA will conduct a fuel test, if alcohol is found, you will be in trouble......I know as I am a pilot. Diesel fuels today are also oxygenated. They have about a 2 year shelf or storage life. I use heating oil in my equipment with an Amsoil additive. Some of my fuel is over 30 years old and still very effective. In fact this past winter, I plowed with my 1976 580 Case at temperatures to -30F.
Ethanol will suspend its own weight in water, so as it carries that water, it will separate and settle to the tank bottom. This creates also another problem in that the ethanol is expected to provide octane and when the petrol floats up to the top, we have the octane separation. Once apart these two fluids cannot remix. Modern electronics will sense problems with detonation and adjust timing and mixture to the best of its ability. Other equipment with static mixture and timing will run improperly and can cause engine damage. By using pure petrol at 90 octane, we ensure reliability and performance for many years in our older outboards, small engines, seasonal equipment and vintage autos.