I am a huge fan of the Ford Festiva from '91 to '93...old enough for OBD 1 testing, simple enough to be easily worked on and so very durable that even a near-destitute person like myself could keep one running-
-until recently that is. On Jan 2nd my beloved Red Menace suffered a full systemic power surge of some sort that cracked open her fusible block, burned up most of her wiring harness and shorted the EGR system-and an estimated $2000+ for a vehicle with over 300K miles on her was just too much for my pocketbook to bear, so i'm riding a used scooter for now and saving up for a tiny truck of some sort (pity I can't find an old Datsun from the early '80's or similar). Good news though- my Landlord wanted a project car so I let him have the Menace for scrap value-the tale of the Red Menace may not yet be finished...
At any rate, my Red Menace was a '93 Festiva, 5-speed with clutch and fuel-injected much like yours. Being a man of tiny wallet my Ecomods were very simple and not very technical:
1) Watched my driving habits-I didn't do much Pulse-and-Glide or close drafting, but I kept to the local speed limits, stopped caring about the idiots passing me at 15MPH over the legal limits and just had fun getting from Point A to Point B.Did my outlook a lot of good,
2) Partial Grill block from lightweight Coroplast. My engine always ran somewhat cool even in Summer so I had a 50% block then and a 75% block in Winter.
3) NC DOT would not let me delete my side mirror but had no issues with letting me replace the stock item with a slimmer one.
4) A set of low-resistance tires set to just over Max sidewall (42 lbs for mine).
5) Tried a body pan but found that my existing bumper skirt was doing almost as well so I got rid of it-it was fun giving it a go though.
6) Kept my spare tire but deleted the entire back seat (I seldom need passenger room and it was torn up anyway) lightening my load by roughly 180 lbs any giving me more cargo space (I swear that poor car thought it was a truck sometimes the way I loaded her...
Despite the fact that I didn't do any of the more involved mods(taller gears, lighter flywheel, cylinder deactivation, different lubricant weights, cylinder hone, aero mods etc etc) I routinely achieved between 49-52 MPG highway and 40-45 MPG city-and this was at 305K on the odometer, shortly before she...passed away (sniff!).
I think your Festiva can quite easily achieve and even surpass my own performance with little effort. As others have mentioned I think that your main issue right now is your very short commute-have you considered a scooter or bicycle for the clear and sunny days and using the car only for bad weather commutes and long trips? That alone should boost you FE considerably(only don't ride a scooter in February, I have little choice but I can tell you IT IS COLD
).
Best of luck with your Festiva-I envy you and wish you all the best.