Read this it's very interesting. Here is somethings from the site. These people are claiming they can acheive hybird MPG with a regular car.
"Section II - Basic FE saving techniques
Now that we have a good feel for what others perceive as a problem without knowing what they themselves are achieving, let us begin to consider the ways to match if not beat the EPA estimates.
Do not use quick accelerations or brake heavily:
This reduces fuel economy by as much as 33 percent at highway speeds and 5 percent around town. EPA tests do not account for this kind of vigorous driving.
Do not idle excessively:
Decreases average FE. The EPA city test includes idling, but drivers that experience more idling experience lower MPG.
Do not drive at higher speeds:
This increases aerodynamic drag (wind resistance) and mechanical friction which reduces fuel economy. The EPA test accounts for aerodynamic drag up to highway speeds of 60 mph, but drivers often exceed this speed.
Cold weather and frequent short trips reduce fuel economy
, since your engine doesn't operate efficiently until it is warmed up. In colder weather, it takes longer for your engine to warm, and on short trips, your vehicle operates a smaller percentage of time at the desired temperature.
Letting your car idle to warm-up doesn't help your fuel economy, it actually uses more fuel and creates more pollution. 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. Vehicles are not tested with additional cargo on the exterior.
Do not tow unless absolutely necessary:
Towing a trailer or carrying excessive weight does decrease fuel economy. Vehicles are assumed to carry three hundred pounds of passengers and cargo in the EPA test cycles.
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:
Driving hilly or mountainous terrain or on unpaved roads reduces fuel economy most of the time. The EPA test assumes vehicles operate over flat ground.
Do not use 4-wheel drive if it is not needed.
4-Wheel drive reduces fuel economy. Four-wheel drive vehicles are tested in 2-wheel drive. Engaging all four wheels makes the engine work harder and increases crankcase losses.
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.
Inherent Variations in Vehicles:
Small variations in the way vehicles are manufactured and assembled can cause MPG variations among vehicles of the same make and model. Usually, differences are small, but a few drivers will see a marked deviation from the EPA estimates.
New vehicles will not obtain their optimal fuel economy until the engine has broken in. This may take 3-5 thousand miles."