I was having paraffin problems, from pump gas. I even had to replace the carb on my Kombi, as it has some internals that I couldn't get cleaned out. I switched to AV100LL fuel and haven't had a single problem, since. I use Klotz 50:1 oil and mix it at that. What I've been told, low-grade (87 octane) is refinery byproduct that has additives put in it to allow it to be burnable. Aviation fuel is pure, as we can't have planes falling out of the sky from crap fuel. Pump gas on your skin takes a couple days to get out. Aviation fuel on your skin lasts seconds and there is absolutely no residual smell. Around here, regular is ~$3.80 per gal, premium is $4+ per gal, AV100LL is $5.50 per gal. It burns cleaner and my stuff noticeably runs better. It's worth the extra expense, to me. BTW, I've cleaned the carb on my little Echo, numerous times. But, it's 11 years old and still going.