Drive only when needed. The best way to reduce the fuel consumption is to simply drive your car less. Drive your car only when you really need to. If you only need to travel a few blocks, consider walking or even riding a bicycle. Not only will you save money at the pump, the exercise will certainly do you some good
Make sure the gas cap is on tight. One reason you may not be getting the mileage you expect is because there isn't as much gas in your tank as you think. 147 million gallons of gas were lost last year due to evaporation. Why did it evaporate? The gas cap was not on tight. So just make sure it is tight, and it will enable you to keep all the gas you pay for
Avoid idling. When you do need to drive your car, make sure you avoid idling whenever possible. When your car is running, but not moving, your gas mileage is absolute zero. So if your car will remain stationary for more than a minute or so, switch the engine off. However, only do this when it is safe to do so
Accelerate and break steadily. While driving, always apply steady and consistent pressure to your car's accelerator pedal. A heavy foot will always result in reduced gas mileage and poor fuel consumption
Drive the speed limit. Always try to drive at or near the speed limit. The optimal traveling speed for every make and model vehicle is different. However, the faster you drive, the worse your gas mileage and fuel consumption will be. Drive as fast as you need to in order to maintain a safe driving speed. But, save highway driving speeds for the highway and not around town
Coast when possible. Constantly accelerating and braking only wastes fuel and reduces your car's fuel consumption. So, whenever possible, coast and avoid burning excess fuel. This takes a little practice, but can be a great way to increase the fuel economy of your vehicle
Use cruise control on the highways. Cruise control means that your car will be going at a constant velocity, which means there is no acceleration. No acceleration reduces the amount of work your engine does, and therefore it uses less gas. You should set your cruise control at the speed limit, because 55 miles per hour is the perfect speed for maximum fuel efficiency
Make your car more aerodynamic. You can do so by removing the roof racks on top of the car, and also by decreasing the weight of the car by taking out unneeded items
Keep the windows closed. The more aerodynamic your vehicle remains, the better your car's fuel efficiency. Keeping your windows down while driving creates more drag and wind resistance for your automobile. If you are driving at speeds of less than 35 mph, it is usually okay to keep the windows down. However, at higher speeds, you should keep the windows up order to reduce drag and improve fuel consumption
Minimize air conditioning. There will be times, of course, when summer heat will cause you to use the air conditioning system. However, use the AC in moderation. If you need to choose between keeping your windows rolled down or using the AC at high speeds, use the air conditioning on a low setting
Replace dirty air filters. Dirty air filters cause your car's engine to work much harder than it has to and always results in poor fuel economy. So, make sure you follow the manufacturer's recommendation for periodically changing out the air filter. A clean air filter allows your engine to perform more efficiently and also helps you save money at the pump
Maintain proper tire inflation. Check your car owner's manual and always ensure your tires are inflated to the proper air pressure level. Improperly inflated tires can reduce your car's fuel economy by up to five percent in some cases. This is quite simply a complete waste of fuel and money
Reduce weight in the vehicle. Get rid of any unnecessary items in your car's trunk or other areas of the vehicle. For every 100 pounds of weight in the vehicle, your car's fuel economy decreases by about one or two percent. By making sure your vehicle remains as light as possible, you can improve the fuel consumption of your vehicle and save money on your fuel bill
Sorry it's really long :P but hope this helped