[note 2: Most of what I write isn't relevant to Instructables. My main blog is here: biodieselhauling.blogspot.com]
[note 3: Also save energy at home. See my energy guide: instructables.com/id/Not-your-average-save-energy-advice-use-less-en/ ]
Go 50-100% farther on a tank of fuel.
Due to its size and weight this truck is considered a commercial vehicle and is exempt from even light-truck CAFE standards. Even so, with the modifications I have made, I am getting higher mileage than CAFE standards for 2009 cars.
I read an article in Mother Jones Magazine about Wayne Gerdes, mileage champion, and was inspired. I have read that people tend to get between 10 and 16mpg on average in the same truck I have. I was getting around 15. After the mods described here, on a recent tank I got 30.28mpg.
The best thing to do is to not drive at all. Ride a bike, take the train, carpool.
If you do drive, buy the absolute smallest car you can. If you only need a big vehicle occasionally, rent one.
I bicycle or use my 70mpg 250cc motorcycle for personal transport, but my truck still gets a lot of miles, so I wanted to make it as fuel efficient as possible.
I use this truck for work, moving up to 3 tons of soil or broken concrete, entire 1 bedroom apartments worth of belongings (including furniture) in a single trip, etc.
I also need something with enough power to move my 7500lb RV trailer (which is also my home - a very efficient way to live: I use as much electricity in a month as the average American home uses in one day)
Most of these steps could be done to any vehicle, increasing mileage from 50% to 100% or more.