One of the easiest ways to improve gas mileage is to check your tire pressure, being sure to keep your tires properly inflated. Low pressure in a tire makes it harder to roll.
How much air should you have in your tires? Typically you’ll find the recommended pressure on a sticker on the inside of the driver’s door jamb. If it’s not there, check in the glove box. The info is also found in the maintenance or car-care section of your vehicle’s owner’s manual.
According to the website fueleconomy.gov, “You can improve your gas mileage by 0.6% on average—up to 3% in some cases—by keeping your tires inflated to the proper pressure. Under-inflated tires can lower gas mileage by about 0.2% for every 1 psi* drop in the average pressure of all tires. Properly inflated tires are safer and last longer.”
How to check your tire pressure
You’ll need a few items:
- an air tank
- a pressure gauge
- paper & writing instrument
1. Start with cold tires
Tires are considered “cold” when the vehicle has been parked for three hours or more, or if the vehicle has been driven less than a mile at moderate speed.
2. Check the manufacturer’s recommended PSI
As mentioned above, look on the driver’s side door jamb or your owner’s manual to find the recommended cold tire PSI for your front and rear tires.
3. Write down the PSI for each tire
If your front and rear tires require different pressure levels, write down the correct PSI for each to avoid getting confused as you move around your vehicle checking tire pressure.
4. Check each tire’s pressure with your gauge
Remove the valve cap from one of your tires. Then place the pressure gauge on the valve stem and press down hard enough so the hissing sound disappears and your gauge provides a reading. With a standard gauge, the air pressure will push a small bar out from the bottom of the gauge. Measurement units are etched into the bar. A digital gauge will show you the reading on a screen.
Write down the reading and repeat this process for all four tires.
5. Fill to the recommended PSI
Use an air compressor to refill any tires with low pressure. Many air compressors are different, so read directions carefully to be sure you’re using it correctly.
If you’re using the air compressor at a gas station, be sure to park so that the hose will reach all four tires. Insert change into the machine until you hear the motor running. Fill each tire by placing the end of the hose over the valve stem and pressing on the lever.
Using a gas station air compressor means your tires might be “hot.” If it is necessary to adjust inflation pressure when tires are “hot”, set their pressure to 4 psi (14 kPa) above the recommended cold inflation pressure. Recheck the inflation pressure when the tires are cold.
After filling your tires, use the gauge to check pressure again. At this point, it’s ok if you overfilled the tires because you can always let some air back out. Never drive on overinflated tires. Overinflation can result in decreased traction, premature wear, and decreased impact absorption.
6. Repeat process monthly
Make the above procedure a monthly ritual. Regularly checking your tire pressure is the best way to ensure your tires never dip far below the optimal PSI.
Check out our Car Care section for more tips on keeping your vehicle performing at its peak.
*Vehicle manufacturers specify PSI – literally “pounds per square inch” of pressure – assuming tires are cold. Tires are considered cold when the vehicle has been parked for three hours or more, or if the vehicle has been driven less than a mile (1.6 km) at moderate speed. PSI is the unit your pressure gauge uses to provide readings.