This is from the Textron Lycoming Engine web site. It is a reprint of maintainance recommendations.
Quote "Turbine fuel, or a mixture of turbine and aviation gasoline, has
proven to be a particularly ruinous fuel for piston engines. As a
result, if the engine has been operated with this unspecified fuel,
qualified maintenance personnel must make a detailed inspection
of the engine with particular attention to the combustion chambers.
If detonation has been severe enough, further damage will
occur to crank pins and main bearings, counterweights and valve
train components. In view of possible damage, disassembly and
inspection of the engine parts is the only safe recommendation
that can be made after the engine has been operated with improper
fuels. If it has been determined that the engine has been run on
unspecified fuel, do not continue to operate it unless it has been
inspected and certified to be airworthy by competent maintenance
personnel.
Lycoming Service Bulletin No. 398 is the latest reference concerning
Lycoming engines which have been operated with
unspecified fuel" Unquote
I would suggest this advice is equally relavent to the ROTAX 912 (note jet fuel and diesel fuel are esssentially equivalent for the purposes of this discussion)