[LocoJason]

Hello! Long time lurker and first time poster here. I've been into cars for as long as I can remember, and I have too many of them.

I purchased a 2000 Ford Focus ZX3 with a manual transmission last year to save on gas with my regular commute and to take on short trips out of state. It was cheap, well maintained, and under 100K miles. I decided on a focus after a lot of research. The Focus is hard (if not impossible) to beat in terms of initial investment cost, replacement parts cost, insurance, and last but not least: fuel economy. With a 25/33 rating, it's not too bad to begin with. I found after just a few weeks of owning it, that I was averaging more like 34mpg on the highway and ~28 around town for a total of 32 combined, and that's ON E10 fuel! Not bad for a car that cost me less than $3000. With ~20K miles per year being my average, the car would actually pay for itself in 3 years vs my previous commuter vehicle. Win-Win.

For many years I had been into performance cars of many types. I never really focused on fuel economy until I bought this Focus. Now, the reasons may not be obvious to all... but here is what pulled me into ecomodding my Focus. The Focus is an extremely slow car from my perspective. It has 130hp... that's 120hp LESS than my next-slowest car.

After a couple very small modifications, addition of a scangauge and some big modification to my driving habits, I now average around 35 mpg per fill-up.

Mods so far:
Front underpanels made from coroplast
Front lower grill opening blocked ~50%
Front tire spats
Tires at 40PSIg
Mobil 1 0w-20 AFE
Lots of coasting/modified driving/scangauge

Now, like most people before getting the scangauge I thought "slower is better, right"? That was very true for other cars of mine in the past... NOPE. Not for this Focus. After reading into it, I found it is apparently not so in all cases; especially with a well-tuned engine. An interesting thing to note is I consistently averaged better fuel economy at 70mph than I do at 65mph. I verified what the scangauge was telling me by continuing to monitor my fill-up MPG's and changing my target highway speeds between fill-ups. This seems counter-intuitive, but I have tested it many times and normally get ~.5mpg better at 70mph. I tested this again (scangauge only) using 60mph vs 65mph when driving back roads. 65mph delivered another .5mpg improvement over 60mph, again showing that the engine was in its prime operating speed/load when the car is closer to 70MPH in 5th gear. I have not tested slower and I still wonder at what speed the aerodynamic drag has reduced enough to offset the lower efficiency of the engine and actually deliver an increase in economy? Maybe around 50 or 45?

I've thought about some of the things that could be done to further improve fuel economy. Engine mods like a custom intake cam, adjustable cam gears, etc. were all major turn-offs to me. Why? This car can hardly get out of its own way as it is, I doubt I could tolerate driving a vehicle much slower.

So that leaves me with aero mods and rolling resistance to focus on...