Fuel efficiency mods

[Caramanos2000]

I am currently averaging around 30mpg in the city with my 2012 se and managed 45mpg on the highway Since this car will never be fast I want to mod it for mpg Here are my ideas, feel free to comment.

1. More psi in tires
2. Extending air dam in front of front tires
3. adding front air dam, either garden edging or garage door seal
4. adding underbody panels to reduce air drag on the carriage
5. considering a more free flowing exhaust but I want it to be as quiet as it is now
6. vortex generators on roof?
7. more free flowing air filter
8. thinking about trying HHO even if just to improve emissions and keeping engine clean
9. switching to 5w-20 in the engine and full synthetic in the gear box
10. Replacing coolant for distilled water and water wetter