John Linden: Hi! I'm John Linden, Master ASE Certified Technician and North America Training Manager for Midas International Corporation. The easiest and quickest way to get better gas mileage out of your vehicle is to properly maintain the tires.
A good tire has at least 830 seconds of an inch of tread life remaining. A tire that is completely worn out only has 230 seconds of an inch remaining. It is a good idea to consider new tires when they were done to around 3 or 430 seconds on an inch. The less tread you have on the tire the greater the chances are your vehicle can hydroplane or slide on the top of water.
While it is best to buy all four tires at the same time, if you buy only two tires they should always be installed on the rear, no matter what type of vehicle you are driving.
Putting the new tires on the rear helps to control the vehicle on wet road, especially around the curve or bend. If a tire is low on air the rolling resistance increases, it takes more energy to move the vehicle. More energy requires more fuel and more fuel means more money out of your pocket.
One of the signs that there could be a problem is if you constantly have to add air. All tires should be checked regularly. A good practice is at least to check them once a month. It's best to check them when they are cold, preferably in the morning to get a more accurate reading.
As the tires get hot from driving, the air inside the tire expands and the pressure increases. So don't be miss lead by the air pressure when the tire is hot. If you have been driving allow at least 20 or 30 minutes before measuring the air pressure. There is no such thing as one air pressure that fits all vehicles. So to find the correct air pressure for your vehicle look on the door placard or in your owner's manual.
Once you know the proper inflation pressure check each tire by removing the valve stem cap and placing the air gauge on the valve stem. Over-inflated tires can cause premature ware, give you a hard ride and cause the tire to bounce excessively.
All vehicles manufactures since 2007 are equipped with a safety feature called a Tire Pressure Monitoring System or TPMS. If the air pressure drops below 25% of the manufacturer's recommended pressure, the TPMS indicator on the dash will illuminate. This system does not let you know if your tires are only 3 or 4 pounds under inflated. So it's important to check them yourself on a regular basis.
Remember to check all the tires, even the spare. If you end up with a flat tire you will need that spare tire and that is not the time to realize that it is low or has no air in it.
So these are some tips on how you can increase fuel efficiency by properly maintaining your tires.