"B A R R Y" wrote in message
et...
Ken Finney wrote:

I already am, but there an STC for diesels in 172s.


Running on Jet-A, not Biodiesel.

AKAIK, Jet-A, Diesel Fuel, and Bio-Diesel all solve the Ethanol problem and
diesel engines have better thermal efficiency.

Actually, in many ways, this whole series of discussions reminds me of a
poster that I used to see as a kid, which said:
"When you're up to your ass in aligators, remember
that you came here to drain the swamp!"

With that in mind, remember that the purpose of the mogas stc's, and the
research leading up to them, was to alleviate the lead-fouling casued by the
use of 100-115LL in some of the older designed low compression engines. It
was a maintenance and reliability issue and was not related to any cost per
gallon spread between avgas and mogas. At that time, IIRC, avgas contained
more lead than it does today.

Also, with that in mind, the modern development of diesel aircraft engines
was a response to the possible, or probably, end of avgas production as
avgas is a small and shrinking market niche and the possibility remains that
leaded fuel could be completely phased out. Ethanol has the octane, but is
problematic (deliberate understatement) to store in aircraft fuel
tanks--even if all to the material compatability issues are resolved. OTOH,
supplies of Jet-A (and Jet-B where applicable) seem assured well into the
future. The greater efficiency of diesel engines is an excellent bonus; but
was not part of the original purpose.

Peter