I think the trend is going in the right direction. Today I drove about 250 miles on a trip. It was all in WV so no flat roads it was all up or down hill. I was driving between 55 and 60mph. No wind and running ethanol free gas Both windows down and the rear wing windows open. I managed to get 65mpg on the trip. I filled up before and after and the numbers matched the mpguino as usual with this car and filling up on the same pump.
For today's trip I was easy on the car and didn't race anyone off the lights, except one time
I think with a few tweaks the car could easily get 70mpg on this trip just driving it easy. If someone was to take this car and go all out hypermiling I bet it would be impressive.
The list of mods I have done to the car:
Weight reduction, no back seat, spare tire/jack, no rear seat belts.
Aero is as shown in this thread
Crower 181 duration cam, ignition at 6 degrees
Yokohama 145/12 tires at 36psi
injector kill switch and engine start button on the shifter
I am really thinking the cam is what is making the mods have a bigger effect than usual. It is a pretty good cam. To really get the car right I need more gearing so either go to 155/13 tires or find a 3.52 trans. This cam basically is out of power at 3000, it's power range is probably 500rpm lower than the stock xfi.
If this car was a bit lighter I think it would be at 70mpg right now. It has a complete non working a/c system, power windows and locks, and 2 layers of soundproofing under the carpet. All that stuff together is probably 100lbs so it offsets the stripping of the interior. The frame horns and important parts of the car are made out of 10ga steel so the car will hopefully never rust out again. For now I will probably just drive it a bit and see where the numbers settle before doing any more mods.
I guess the next step is to work on a belly pan but that will have to wait till I get some more free time.