According to the National Highway Traffic Safety Administration (NHTSA), tires can lose up to half their air pressure before they actually appear to casual observers to be underinflated.
Proper Tire Pressure Can Reduce Your Carbon Footprint. Properly inflated tires have a positive environmental impact by releasing less carbon dioxide (CO2) into the atmosphere through better fuel efficiency. A reduction in CO2 emissions contributes to reducing greenhouse gas emissions.
Direct TPMS systems utilize radio frequency (RF) technology to transmit pressure data and other information to the vehicle's electronic control unit (ECU).
In the U.S., if you purchased a car or light duty vehicle under 10,000 lbs, manufactured after September 1, 2007, you have TPMS. If your model was manufactured after October 5, 2005, you may have TPMS.