[philipkglass]

Running lean, highly compressed, and highly efficient reduces expected production of carbon monoxide and residual hydrocarbons. But it significantly increases nitrogen oxide formation, as in diesel engines. So I wonder how the emissions control system deals with the extra NOx -- that has (see Dieselgate and continuing related fallout) proven quite a sticky problem for high efficiency diesel engines in passenger vehicles. The cheap "solutions" were mostly cheats and the actual solutions cost more.