Rotax recommends some 100LL for valve lubrication

Hello James

Interesting article!

Please review the latest Rotax Service instruction regarding the Selection of suitable operating fluids for ROTAX® Engine Type 916 iSc B, 915 i A/B (Series), 912 i (Series), 912 and 914 (Series) - https://legacy.rotaxowner.com/si_tb_info/serviceinfo/si-914-019-r11.pdf

On page 12 it states the following:

NOTE:

"AVGAS 100LL places greater stress on the valve due to its high lead content and forms increased deposits in the combustion chamber and lead sediments in the oil system."

So which is it?  "Provides [valve] lubrication" or "places greater stress on the valve" ?  I thought lubrication generally decreased "stress".

Can you provide a link to that report?

The attached file is the chapter on fuels.

That's an interesting chapter.  Thanks!  

What jumps out at me are his footnotes about Lycoming and Continental, e.g.

8  See https://www.lycoming.com/service-instruction-no-1070-AB.

9  Personal communication, Christopher Pollitt, Continental, April 28, 2020.

But then... no mention of where he got his information about Rotax suggesting occasional use of 100LL!  If it's something Rotax has published, why not quote that?  Or indeed, if it were just a conversation with someone at Rotax, why not footnote that?

When someone says something surprising like that, you would expect them to back it up with some evidence, especially when it seems at odds with information that Rotax has officially published... I'm a skeptic.

I also take issue with much of what he says about "mogas".  It is still perfectly feasible, both economically and otherwise, for refiners to NOT blend ethanol with their "intermediate stock" premium product, which typically is then sold as 91AKI E0.  This is available at many filling stations in my area (upper Hudson valley).

He also mentions AirNav as his main source for airports where "mogas" is sold.  I have found AirNav to be completely unreliable in this regard.  Much better is http://flyunleaded.com/airports.html