Thanks Aviator, it makes sense.
I guess the pros are:
Lower weight. This can be a big deal in the flying I am interested in
Higher output? More rpm and torque I'd guess. Could also be a big deal if a smaller engine would spool up the same prop at the same rpm and mid range
Cons:
A little higher expense for fuel
A little more slime? It looks like around 3% oil in the mix of the type used in glow engines
Glow plug fouling after X runs? Spark plug will run at least one season (maybe 400 flights) using avgas. The lead needs cleaning after 15 gallons or so
I have an OS 15cc ignition engine now that is a bit anemic on gas alone. Sweet runner and super quiet on the stock muffler but power is just so so. I may have to take a look at what can be done with this engine.