Maintaining the optimum value of the air pressure in your tire will help you to save fuel consumptions from to 10% to 15%. Each car manufacturer recommend the amount of air pressure you should have in your tires, to find these values; open the car door (next to steering) and look for any labels on the edge of the car and read the values. You will have two values, one if the load is light and the other if the car is fully loaded. Check your air pressure on the tires every 3 weeks to one months so you can minimize the fuel consumptions.