I used to drive a 1996 VW Passat. If I drove reasonably on the highway, I could average about 57 mpg per tank. I thought that was great, so my next car was a 2006 VW Jetta. That car only got 40 mpg at its best, but that was pretty good comparatively, so I accepted it. The newer TDIs were rated even lower, and then mostly went away, so I got a Honda. It only gets 23 mpg. Each of these cars has also been shorter between maintenance cycles, and with a shorter overall expected lifespan. I don't know what's going on with the regulatory landscape that cars keep getting bigger, heavier, and less efficient (by mile), but it seems like there's plenty of room for improvement. The fact that this is proposed by automakers, though, makes me extremely skeptical.