Tire Pressure
Maintaining correct tire pressure in all tires of your car can be very rewarding. Driving on under-pressured tires significantly reduces the tire life, acceleration, braking, maneuverability, traction and all these combine together to hugely affect your gas consumption. This means driving on under-pressured tires makes your ride consume way more fuel.
Air-Conditioner
Wait a minute! Think twice before blasting the air conditioner. Scientifically, cars running with the A/C on consume about 20% more fuel, or more. That means if you're currently spending $2000 on fuel a year, you could actually be spending no more than just $1600 !
Acceleration
The light turns green and the pedal's to the metal. Be careful NOT to accelerate swiftly unless under emergency situations. Hard acceleration makes fuel move faster to the engine and thus it consumes at least 5% more fuel on a wider scale.
Braking
Be aware of hazardous drivers and driving conditions on the road so as to avoid strong braking. In most cars equipped with ABS & EBD, hard braking forces the vehicle's mechanism to suddenly drink a little extra fuel from the reservoir. Although, if you brake normally you can save as much as another 5% on fuel.
Driving a Cold Car
Its winter and you're shivering. So is your car. Be careful not to drive a cold car (check the engine temperature on the speedometer) too fast and absolutely avoid revving the engine more than 2-3k RPM until the engine temperature reaches half way to the normal. Let the engine oil flow up when the car is really cold, which means let it run for at least 2-3 minutes on a cold morning before driving it.
Fill When it's a Bit Cooler Outside
Fill the tank when the temperature is a bit cooler outside. Therefore, when the temperature resumes to normal, actually you have a little more gas in your tank! May not be very beneficial, but maybe something to consider.
Don't Carry Unnecessary Weight
Make sure the your back seats, dashboard and trunk are not loaded with unnecessary things weighing the car down. For example, carrying bulky snow-chains for 18" wheels in Arizona's July unnecessarily weighs your car down and makes it consume more fuel for the same acceleration and braking. Don't carry things you don't need.
Change Your Engine Oil
Check the oil dipstick on the engine face every 1000 miles or so to make sure the engine oil level is normal and the oil condition is good. Running an engine with not enough oil forces the engine to use more fuel from the tank. Instead, if you change the oil regularly you can save a bit on gas and enjoy a stronger engine along with a more comfortable ride.
Drive With Half a Tank of Gas
Related to the "weight" paragraph above, it may be smart to drive with just a half tank of gas like most people do in some northern European states. As the weight of the car reduces, the fuel efficiency increases and thus you end up with a more efficient engine.
Thanks.
Jerry