Green Car Congress: Mazdas new SKYACTIV gasoline and diesel engines are steps on the road to its Ideal Engine; focus on compression ratio
Maybe one of these days they will actually get to 60% thermanl efficiency with IC engines, and maybe they can do that and pass emissions without aftertreatment. This is what Mazda said in the linked article (60%).
I can only imagine what that would mean in a vehicle like we are talking about here.
regards
Mech