100LL should not cause plugs or rings to gum up. It works great in airplanes. The mix ratio of fuel to oil may need to be adjusted to compensate for different burning techniques. I have ran 100LL in a stock 7.5 mercury outboard motor with mixed fuel/oil and it performed much better than the regular pump gas. It ran smoother and would get up on step faster. I have also ran race gas (120 - 130 octane) on a stock 1999 RM125. The difference in performance was outstanding. Again, the performance and smoothness increased compared to running pump gas (87 or 93 octane). The thing that most effects the performance, smoothness, and how clean the engine runs is the fuel mixture. Rich=Cold=unburned fuel, also when the mixture is rich, there is more oil getting into the engine. Lean=Hot=complete fuel burn, but less oil to the engine. It is a balancing act between fuel burn temperature, oil ratio, and fuel mixture. As far as why the engines run better with the higher octane....my thinking is that the high octane shoves the piston down while the lower octane kicks the piston down. The shove (high octane) provides better combustion harmonics that translate into power and smoothness. The application determines whether the extra performance is worth the extra cost. My 2 cents.