My 2 cents worth. I've been running alcohol for over 30 years, the early part was in 2-smokes, so it had an upper lube in it. Since going to a 4-stroke in 1991, I've been using Klotz Uplon upper lube, KL-107. The very first line on the directions says: Eliminates the need to purge the fuel system. I have, on occasion, had problems, and most of the time, was able to track it back to bad fuel. I did, one time last year, ran out of Klotz, and used another brand, and almost instantly had nozzles and filters plugged, thought it was bad fuel, got some fresh, tested it, ck'd OK, put in the "other" upper lube, still the same problem, so I put more filters in, and almost instantly, they stopped up ,and all the while, I had been flushing the system. Finally went back to Klotz, cleaned the system, again, and now, we've only had anything in the nozzles once, since then. Alcohol draws moisture, it's most common use is to dry propane, so ya gotta be careful on the fuel. I used to flush the system as soon as I got home, then that got to be a hassle, so I quit, I usually leave the system wet. Guess that's more than 2 cents, maybe a nickle. Before we get into what's best, and what's not, I want to make it clear, this is what I do, and it works for me. I just pulled the nozzles, after setting for 2 weeks, in this humidity, they were still "wet", the fuel in them smelled good, and they were clear. I usually "flow" them a couple times a year, using my leak-down cker, and compare them to each other, this set is now probably 6-8 years old, and they are still like new, flow wise anyway. And another thing, I have found, that if I shut the engine down with the kill switch, then shut the fuel off, instead of shutting the fuel off, and letting the metering valve and nozzles run dry, this not only helps "startability", but leaves that part of the system, also "wet", and doesn't dry and turn white, just don't leave it set so long, it starts to jell.