Tire Pressure - Wheels and Tires
Air Pressure
CHECK YOUR AIR PRESSURE
On average, a tire will lose 1 psi of air per month. If you read nothing else on this site, please read that. The tires are the only point of contact with the road. No one part on any car affects the way the car handles, rides, accelerates, and brakes more than the tires.
When you car's tires are under-inflated, it takes much more effort to roll them. This in turn will directly affect your vehicle's fuel efficiency. Thus, inflating your tires to the manufacturer's recommended air pressure is extremely important.
While you can exceed this limit, it is critical to not exceed the maximum cold inflation rating on the tire itself. While adding more air to your tires will improve its MPG (miles per gallon), it may have negative effects on your ride quality, cornering, and braking. Under and over inflation also affect the way your tires wear, and could cause premature tire wear.
Fueleconomy.gov points out that every 1 psi of air pressure in your tires is good for around 3% better gas mileage. It is important to remember not to exceed the tire manufacturer's maximum psi limit.
Air Pressure Gauge
It's smart to have a good air pressure gauge. Don't think that cheap plastic one currently in you glove box is what we're talking about. Digital gauges are good, but they are flimsy plastic, and require a battery. A mechanical air pressure gauge like the following is best:
Click here for product information
For more information, please check this checklist guide to Tire Rack. You'll find most tire stores you go to have the Tire Rack book, so why not just go direct. They will even ship them to a certified installer.
Do performance tires with stiffer side walls produce higher MPGs?
Other tires designed to get better MPGs
Further Reading:
LA Times Article on tires and their effects.