Many of the MPG winds of the 90s and 00s were eaten back up by mandated safety standards. A 2020 focus weighs 10-20% more than a 2000 MY one, for example.

My 1998 SC2 Weighed ~2400 pounds and got MPG in the low 30s (35+ on the highway).

> NOx emissions

Managing that often impacts fuel economy. Ask VW group =)