Speaking for my self I had an 582 that I did run on Avgas all the time for the better part of 11 years flying to and throw from Insfail too weipa Rocky with out a single engine fail I now own a sport Parasol but only run unleaded because I dont have the ablity to avgas but I found that the 582 ran a lot better and the EGT ran cooler never did I have a fouled plug the engine would run a lot smover and more response my lightwing would easly out climb most other 912 single up would climb @ 1000-1200 fpm two up around 600 -700 no problems I am that inpressed with the 582 that I just bought enother too start rebuilding with the help of Carlo Prete, and will be making all the upgrades too mount a four stroke engine but for now will stick with the 582 .
I am looking at the Viking engine with a bit more reseach on the new engines will see what the future holds because they are better for long haul " less mixing of fuels " :1st:
update
may not be able to use a Viking because of the rules