rotorrookie,
This is a great thread, fear not, and thanks for your contribution to it! That was too good a snipe to pass up!
The data on the Deltahawk engines show them at the same weight as the equivilent HP gas engine, which is closer to what we could expect. The estimates about overhaul costs also seem very low, since these engines are turbocharged, which brings a pretty fine set of components into the game, despite the simplicity of the deisel itself.
The Mistral engines are much lighter, but they are rotary engines, and no rotory can achieve the fuel efficiency of a piston engine, so I would expect their fuel burn to be like a gas engine or perhaps a bit higher. I note that they don't publish any fuel figures (or did I miss them?) Also, rotary tip seals have not yet been perfected, I think (but have no recent data on).
If these engines can pass the cert tests, and show good reliability in the field, they can certainly liven up the field for our piston members!