As I mentioned, Rotax allow for a the 80hp to be operated on 90 RON, however further reading indicates, to me, that using such low RON fuel brings with it "knock" risks, that need to be understood & managed.
Using higher RON fuel, reduces the risk.
I am not familiar with the 80 hp, however am aware that, in the 100hp, using 98 RON would seem to near eliminate the risk of "knock" . Check out the Operators Manual Page 5-8
5.1.1) Power setting
Sorry cant seem to copy the attached graph.
You might also like to look up Rotax Service Bulletin (SB) SB-912-079 R1 (same graph appears in this publication)
Additional thought; I understand that higher RON fuels allow for better altitude performance. What this might mean for a Rotax 912 being operated below 10,000ft is not entirely clear to me.
LAME's, L2's, well meaning friend, Forum advisors (me) -
Always listen to their advise BUT they are human, just like the rest of us.
They can be reluctant to give up cherished beliefs (myths) and make errors.
Can be unduly attached to the maintenance/operating doctrine of one engine type (LYCon?) that is then applied to another (Rotax?) without real understanding of the differences.
As PIC/maintainer its your responsibility to decide how to look after (fuel type) your aircraft.
Treat all advise with scepticism - apply your own experince /logic and if all else fails, follow the Rotax advise, as writen in various Manuals & SB,s
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