I have a small engine mechanic that lives up the block and few year ago he did an experiment with both Stable and Seafoam, He had a couple of large relish jars and put stable treated gas in one and Seafoam treated gas in the other and let them sit over the fall and winter and into the spring, The gas in the jar with the Stable treatment turned a darker color then the jar with the Seafoam but they both had a funky smell and the strangest thing was the stable treated jar had a thin film of water at the bottom maybe a 1/16th inch and the one with the Seafoam did not. So he put them on a shelf and let them just sit over the summer. That fall the gas in both had turned even darker in color and they both smelled really bad, the Stable jar had a thicker amount of now almost ugly black water in it and the Seafoam had a thin layer of some dark stuff at the bottom. He poured each jar out into another jar and the Stable jar left a layer of hard brownish black stuff on the bottom of the jar and the Seafoam jar also left a layer of black stuff on the bottom. He then put some fresh gas in both jars and gave them a shake, the stable jar still had the black stuff on the bottom but the Seafoam jar had nothing, the fresh gas dissolved whatever it was away. Result. They both smelled terrible, the Seafoam jar cleaned up whatever that stuff was, he put some in a mower tank and they both ran his old lawn mower, it was hard to start with both but it ran. Thought you might like to know the results of this unscientific experiment. Our thoughts, if you are gonna let it sit, dump the gas out and run the motor till it quits.
1991 Silver Eagle 32 ft sitting on an Oshkosh Frame w/Ford Carbureted Big Block