Never sell land, cars or guns.
If you do sell a car, it has to go far away so you never see it again. Like an ex-girlfriend.
I had a commute for a few years that was 35 miles each way and I drove my '91 Renegade every day. Upgraded the air intake, a better coil, good spark plugs, exhaust upgrade, synthetic lube for everything, 170 degree thermostat and running 33x9.5 BFG All Terrains (I figured skinny tires = less rolling resistance, and I could still go off road; it worked, my records prove it). I'm nuts about my Renegade, and I have recorded every fill up since I bought it brand new to keep track of the mileage and what affect changes had on the mileage by using vehicle expense record books (available at office supply stored for $1-2). Since the majority of the driving was highway, I consistently received an average of 20 MPG as I was able to keep it at 55/65 most of the trip. Add in that the speedo and odometer were actually reading less than the distance/speed I was traveling (since I never adjusted the ratio to the speedo), the actual mileage was better. All the changes were not done all at once, but rather as normal maintenance.
The most surprising thing about my whole experiment was how the winter oxygenated fuel dropped my mileage from 19/20 to 16/17 when the gas stations switched over. Not a huge difference, but I could tell by my numbers and that I'd be short a day on the fill up schedule in the winter.
Part of the mileage was also driving habits. Downhill coasting in neutral, light throttle, etc. It takes an attitude adjustment to not have to race everywhere and give yourself time to get there. Not that I blocked traffic, but there just was no reason to race ahead since I could do the commute at 6am and return trip was around 3pm. When someone wants to race ahead, move over, smile, and think "please, find the police for me".
No, I'm not a "save the world greeine"; just cheap.