I too, run my outbound all the way out of gas, and if I'm leaving it for long, I even open the bowl drain on the carb for a moment and drain the last bit out.Sent from my T-Mobile 4G LTE Device -------- Original message --------From: Josh Muckley via CnC-List <cnc-list@cnc-list.com> Date: 6/13/20 11:10 AM (GMT-05:00) To: C&C List <cnc-list@cnc-list.com> Cc: Josh Muckley <muckl...@gmail.com> Subject: Re: Stus-List Roll-Up Inflatable Dinghies and Motors Bruce,I too have NOT been made aware of Supreme/93 octane being made by default without ethanol. The octane rating is often achieved by simply adding toluene. I've even seen plans for toluene injection systems designed for performance vehicles. As I understand it the octane doesn't add power or BTUs/gallon but rather changes the likelihood of combustion due to the heat of compression (ping/pre-detonation). I'll look for a better explanation and post back. Anecdotally, I exclusively use 93 octane in ALL my applications and I have had small engines with what seem to be trouble due to "stale" gas. In many cases they had had previous owners so it is unknown exactly what caused the problems or if it was simply age related. The latest was a chainsaw which was ~30 years old (my late father's). I didn't perform an autopsy but just simply replaced the carb. During the replacement I found all of the rubber parts to be in remarkably good condition with the exception of the impulse fuel line which kinda disintegrated upon removal.With the Mantis Tiller I've shown before, I found the rubber diaphragms to be cracked and taking a set. Again, previous owners could have done anything so who knows. I've also had two 5Hp Briggs and Stratton engines which sat for years with old gas in the carb. They had clear signs of deposits and varnish which degraded their performance until it was cleaned up. These 2 specific engines were in my care (or lack there of) since new. I don't buy low octane gas so the octane could not have simply been the cause. As a side note the first 2 engines were 2 stroke and the second 2 were 4 stroke. My diagnosis is that each pair may have experienced 2 different failure mechanisms. In the first 2, the degradation of the rubber and plastic-ish parts. This is consistent with ethanol related failures. In the second 2, it appeared that varnish/deposits had developed and clogged the small ports and orifices. This is consistent with allowing the gas to remain in the system and ultimately evaporating, leaving behind the normally low concentrations of non-volatile substances as deposits. This effect is what I believe makes up the varnish. In cleaning these deposits I found that carb cleaner was more or less ineffective and that mechanical removal was necessary.Oddly, I believe that both of these failure mechanisms can be prevented by "running out" the fuel when done using the equipment. Don't just turn of the engine but rather starve it out by shutting of the gas. There may be something to be said about the oil in 2 stroke fuel helping to prevent evaporation and the formation of deposits. Who knows.Josh Muckley S/V Sea Hawk 1989 C&C 37+Solomons, MDOn Sat, Jun 13, 2020, 10:16 bwhitmore via CnC-List <cnc-list@cnc-list.com> wrote:I don't agree, at least here in the U.S. that premium gas doesn't have ethanol in it. There are, however, gas stations that have a pump reserved for non-ethanol gas. Bruce Sent from Samsung tablet._______________________________________________
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