Rotax 912ULS Fuel

The higher compression "S" engine is supposed to be fed 91 octane (AKI) minimum, to preclude detonation.  He would be wiser to accept fuel containing ethanol (with associated higher octane) than to continue to use the 87, presumably because it's E0 (or just cheaper?).

Refer him to the current version of the Operator's Manual.

The other guy is asking for a serious money problem in the tune of $5k-$10k. Could even mean a new engine for $18K.  He may be getting by with the lower octane for now, but there will be a flight where things will line up  line up just right and he'll end up with detonation and destroy cylinders and pistons. This isn't a matter of if, but when. You can tell him he's wrong and show him in the manual and in SB's, but some people will think they know more than Rotax.

You just do the right thing and keep in eye on the other guy.

Remember what everyone always says: That never happened before.  Your answer: Yep, but now it has.

Thank you Tyler and Roger,

I have forwarded the information to my friend and I am sure he will make the necessary adjustment in Octane.  I really appreciate both of you for taking the time to respond.  You may have saved a life.

Regards,

William Campbell