The weight issue is no longer such a big deal - I would hesitate to use Zoche as an example - he has spent more money on attending Oskhosh than on developing his engines! However if you look at the Thielert it has a similar firewall forward weight to an O-320. The Thielert is 135 hp and obviously the Lycoming 160. Once you are over 3000' then the Thielert is more powerful. Now given that the Thielert is a Mercedes conversion the arguments about diesels being a lot heavier seem to fall to bits.. .Dedicated designs, I suppose the Wilksh is closest at the moment should be a lot lighter - the 120hp wilksch has a target weight of 100kg, versus the 137 kg of the Thielert.. .Even the Renault engines are said not to be much heavier - and the fuel burn is so much lower that the extra weight is not a handicap.. .Given European fuel costs there is a real need for these fuels - lets hope the rumour is true!