A German Mooney association is conducting a survey trying to gauge interest for a diesel conversion: Visit http://www.mooney.de/diesel/index-en.html They say: The topic diesel engines for general aviation aircrafts has been discussed several times in the last years and is still a very hot topic. The improvements in diesel engines for GA aircrafts is very obvious and the list of planes that can be converted to a diesel engine grows continuously. Also some of the Mooney-owners of our Community often play with the idea of a diesel conversion when they come to TBO. But soon they realize that there is still no alternative to the old, Avgas engine and the conversion simply stays a dream. First of all there still is no engine that would fit within the performance class of a Mooney. A Mooney with a Thielert 135HP engine, like Robin, Piper or Cessna do it, is no option. As for the Thielert four liter V8 engine, it might fit into a Duke, but definitely not in a Mooney. Not every engine would fit into its tight cowling. Also the engine weight will be very critical, as the Mooney is already very heavy on the nose gear and will not take much more weight in the front. This fact also prevents the SMA O-305 engine from being an option. It is the only engine that - with 230 HP - would fit into the performance class of many Mooneys, but it is about 50 kg (110 lbs) heavier than our current Lycomings and therefore an absolute NO-GO for the Mooney! So what can you do in this case? One option would be to be satisfied with the current situation and stay with the old engine. Another option would be, to wait until something might happen on its own and the third option would be to do something yourself. We decided for the last option and would like to find out, which possibilities are available for our Mooneys and what can be done today.