I've spent about 2 1/2 years honing my driving habits to minimize fuel consumption - first in a Grand Cherokee Limited, now in a Land Rover LR3 HSE. Admittedly, not the first vehicles to come to mind when thinking about fuel efficiency (except in a negative way). They're owned by my company. But I've gotten much higher than EPA ratings in both vehicles - I'm currently at 21 m.p.g. in the LR3.
The problem is, as detailed at
http://hamiltonianfunction.blogspot....5/so-what.html and at
http://hamiltonianfunction.blogspot....i-thought.html, the time expenditure of this type of driving this way is huge. It amounts to a week of vacation each year, and the avoided cost of fuel doesn't come near the amount my company pays me for the time lost. Now I'm on salary and get all my work done, so the company doesn't REALLY pay for it - I do. So I have to look at it as a hobby. But the fact is, when you run the numbers (I did so for the Cherokee at
http://hamiltonianfunction.blogspot....est-speed.html), it turns out that for most situations on the highway, if your time is worth much, speeding is better.
For information, my commute is a little over 60 miles per day round trip, about 80% on Southern California freeways.
I've tried using the mobile phone and my assistant, learning Mandarin from podcasts, etc. but the fact is, I'm most productive sitting at my desk or meeting with clients. Dr. Steven Dutch (great bunch of pages by the way) comes to a similar conclusion regarding public transportation at
http://www.uwgb.edu/dutchs/PSEUDOSC/MassTransit.HTM.
In any case, it's a fun hobby, but the economics don't pan out, at least in my vehicle.