By 2008, the government has mandated that all new vehicles will be required to warn consumers when a tire is underinflated through a light in the vehicle’s instrument cluster.However, it’s a good idea to check your fleet and personal vehicles’ tire pressures right now, for safety and to improve fuel consumption by at least two percent. Here are some do’s and don’ts from on how to measure tire pressure properly from AAA:--When you buy new tires, your best inflation pressure guideline is the maximum pressure molded into the tire sidewall.--The pressure should be checked and adjusted when the tire is completely cold or after driving less than one mile. The pressure in a tire rises as the vehicle is driven. Never let air out of a hot tire to reduce pressure to a cold-inflation recommendation.-- If you go higher than the carmaker's specs, hold it to no more than 4 psi and do not exceed the tire's maximum pressure rating.--Myth: the sidewalls of radial tires are supposed to bulge. That may have made a case in 1968 when radials were built with higher profiles and ran at 32-psi pressure. Today, with higher-pressure 50-, 60- and 70-series low-profile radials, that old myth is simply not true. --Don't rely on the pressure gauges on service station air hoses. They are notoriously inaccurate (not to mention hard to read).-- When you buy a pressure gauge, get one that measures up to 50 pounds per square inch (psi) in 1-psi increments. If you have a light- or medium-duty truck or SUV, you may want a gauge that reads up to 80 or 100 psi.