Into the weeds engine design for fuel efficiency discussion.

I'm kinda confused since every car manufacturer in the past 20...oh maybe 35 years has been forced by government to raise fuel efficiency and in doing so they have come up with all kinds of technology such as knock sensors, variable valve timing, so on and so forth. I looked up the Diplomat and they were built between 76-89. Maybe I'm missing something but perhaps purchase a newer car?
If only I could have thought of that...:BangHead: