Clipped from other sources…
Some Tips on how to get more of your money’s worth for every gallon of Gasoline…
Only buy or fill up your car or truck in the early morning when the ground temperature is still cold. Remember that all service stations have their storage tanks buried below ground. The colder the ground the more dense the gasoline, when it gets warmer gasoline expands, so buying in the afternoon or in the evening…your gallon is not exactly a gallon. In the petroleum business, the specific gravity and the temperature of the gasoline, diesel and jet fuel, ethanol and other petroleum products plays an important role.
A 1-degree rise in temperature is a big deal for this business. But the service stations do not have temperature compensation at the pumps.
One of the most important tips is to fill up when your gas tank is HALF FULL or HALF EMPTY. The reason for this is, the more gas you have in your tank the less air occupying its empty space. Gasoline evaporates faster than you can imagine. Gasoline storage tanks have an internal floating roof. This roof serves as zero clearance between the gas and the atmosphere, so it minimizes the evaporation. Unlike service stations, here where I work, every truck that we load is temperature compensated so that every gallon is actually the exact amount.
Another reminder, if there is a gasoline truck pumping into the storage tanks when you stop to buy gas, DO NOT fill up–most likely the gasoline is being stirred up as the gas is being delivered, and you might pick up some of the dirt that normally settles on the bottom. Hope this will help you get the most value for your money
Basic Driving Fuel saving techniques:
Do not idle excessively: Decreases average Fuel Economy (FE).
Do not drive at higher speeds: This increases aerodynamic drag (wind resistance) and mechanical friction which reduces fuel economy.
Cold weather and frequent short trips reduce fuel economy, since your engine doesn’t operate efficiently until it is warmed up. Drive to your furthest destination first and then as you are heading home, stop at the closer destinations in order from furthest to closest as the car is warmed up for longer portions of your drive.
Remove Cargo or cargo racks: Cargo and/or racks on top of your vehicle (e.g., cargo boxes, canoes, etc.) increase aerodynamic drag and lower FE.
Do not tow unless absolutely necessary
Minimize running mechanical and electrical accessories: Running mechanical and electrical accessories (e.g., air conditioner) decreases fuel economy. Operating the air conditioner on “Max” can reduce MPG by roughly 5-25% compared to not using it.
Avoid driving on hilly or mountainous terrain if possible:
Do not use 4-wheel drive if it is not needed.
Maintain your Automobile: A poorly tuned engine burns more fuel, so fuel economy will suffer if it is not in tune. Improperly aligned or under inflated tires can lower fuel economy, as can a dirty air filter or brake drag.
Try to purchase high BTU content gasoline if available: Fuels Vary in Energy Content and some fuels contain less energy than others. Using oxygenated fuels or reformulated gasoline (RFG), can cause a small decrease (1-3%) in fuel economy. In addition, the energy content of gasoline varies from season to season. Typical summer conventional gasoline contains about 1.7% more energy than typical winter conventional gasoline.
More info - Search Google: hypermiling
Or try
http://www.cleanmpg.com/
http://www.cleanmpg.com/forums/showthread.php?s=104d0eb7072fd63c3baa7c452b7c5ce3&t=1510