hi,
we have a K model now for several years in a group..
we have fitted a couple of engines over time , but two years ago fitted a diesel engine. it is FADEC, and though i was doubtful of the wisdom of such an expensive conversion to an oldish aircraft, no one in our group would go back to an avgas engine ( its so hard to get avgas at times and JET A1 is easy), but the main benefit is it has cut our operating cost ( fixed charges excepted ) by 2/3..
50% power will give 80 knots and 3.5 gallons per hour...70% about 90 knots and guzzles...!!!!...5.1 gallons per ( if memory serves correctly ).
i have some fun filing my flight plans...telling atc ( even with standard tanks )'' endurance six hours..!!!''....and when they query and ask would i recheck that saying..'' oops, sorry you're right...it should be seven hours''..!!!!!
it is an expensive job especially at a time when you have the cost of buying but you should consider it in the long run...or better still...buy one now with a time expired engine ( so you're not paying for an engine ) and do the conversion now...
good luck and have fun...
the dean.