Keep your vehicle well maintained.
This is a very basic step, yet it is a routine that many people have gotten out of. These days people have so many other things going on that they often don't maintain their vehicle like they should. They wait until something breaks to fix it, instead of doing preventative maintenance. Your owner's manual will have a list of items that need to be maintained along with the mileage that the maintenance that should be performed. This will include everything from oil changes, replacing belts and hoses, to rotating your tires. If you keep up with the maintenance properly, not only will you improve your gas mileage, but you will also save on costly repairs down the road. It is a lot easier and cheaper to keep your vehicle well maintained than it is to fix it once it breaks.
Keep your vehicle's tires properly inflated.
This is the step that people hear most often, because it can have a great impact on your fuel economy. You will find the proper inflation pressure located on a sticker or metal plate on the driver's door jamb. Keep in mind that most repair shops just inflate tires on cars to about 32 PSI (Pounds per Square Inch), and about 35 PSI for trucks. This is not terrible, however the vehicle manufacturer has done extensive testing with different inflation pressures for your vehicle to find which pressure works the best, and it is not always 32 or 35 PSI. Your vehicle's recommended tire inflation pressure may only be 29 PSI for example. It is also important to have the recommended tire size for your vehicle. This information can also be found on the tire information sticker. Also make sure that all of the tires are the same, as different tires do not work as well together as a matched set. If you own a hybrid vehicle make sure that you check with your owner's manual or a repair shop to see which tires are best for your vehicle. Some hybrid vehicles use different tires than a normal vehicle. These tires offer less rolling resistance than normal tires. If you put regular tires on a hybrid you will notice that your gas mileage has decreased.
If your "Check Engine" light is on, take your car to a mechanic as soon as you can. Some vehicles have a picture of an engine, others have the words "Check Engine" or "Service Engine Soon". They are usually yellow or orange in color. The check engine light comes on to alert you to the fact that something is not working properly. It is also known as a "MIL", or Malfunction Indicator Light. If your check engine light is on then your vehicle is not running as efficiently as it should, and your gas mileage will suffer. While you don't have to worry about damaging your engine, it is best to have your vehicle checked as early as possible. However, if your check engine light starts flashing, then you should get your vehicle to a repair shop immediately. It would be best to have it towed. If the check engine light is flashing it means that the vehicle is misfiring, or skipping, bad enough to cause damage to the catalytic converter, which can result in a costly repair.
Combine errands into a single trip and plan your route ahead of time.
Vehicles run more efficiently when they are at normal operating temperature. If you go to the store, then return home for an hour, and then go to the post office your vehicle will not be as efficient as it would be if you combined the trips. If you can, plan your route to use the interstate or highway as much as possible. This will avoid making as many stops at traffic lights and stop signs. Stop and go driving decreases your gas mileage significantly. However, there are times when it is not feasible to use the interstate, and you have to use surface streets to get around. To get the best gas mileage off of the interstate, plan your entire route before you run your errands. While planning, try to include as many right turns in your route as possible. This is something that most people do not consider. The benefit is that in most places you can make a right turn at a red light without waiting for a green light. Therefore, you will spend less time idling in traffic which is where most of your gas is wasted by being burned without moving.