Maintaining optimum tire pressure will prove one of the easiest ways in which a driver can save on fuel costs. Many tire dealerships will perform this chore for free and add air to any tire that needs it. Correct air pressure can vary markedly, depending on the size and strength of the tires.
With all the tires on a vehicle carrying the correct air pressure, less tire-to-pavement friction occurs. This has an immediate and beneficial effect on the fuel efficiency of the vehicle.
Bottom line: For personal safety as well as increased fuel efficiency, make sure to maintain the correct air pressure in all the tires on your vehicle.