Today I was speaking to another 8 cylinder Jab owner who stated that due to the higher compression ratio of the 8 that Avgas must be used.
So far (23 hours) I have used ultra unleaded 98 and it has performed quite well.
I am aware of the basic points for and against but what is the best regime for the long term health of the engine?
What are others out there using?
The Installation manual for the 5100 says 100 RON or over, which in Australia could mean the really fancy MOGAS (Shell and I think BP do 100 RON MOGAS) or AVGAS.
Personally I've found that the higher-octane MOGAS goes stale pretty quickly, especially in a vented tank - my dirt bike would be hard to start after sitting for anything more than about a week using those fuels and the fix was to get some fresh fuel into it. So unless I was flying a lot, I'd lean towards AVGAS. That said, MOGAS burns much cleaner than AVGAS - a very good thing - so it isn't totally out of the question if you manage take care how you manage/use it.