If the pressure is lower than the recommended, use the 4-way tire inflator to add air. Attach the nozzle to the valve stem and flip the switch on the inflator to the "inflate" setting. Watch the gauge while adding in a little air at a time, periodically checking the pressure. The pressure gauge on this 4-way tire inflator provides real-time monitoring to prevent over-inflation. Properly inflated tires increase fuel efficiency, improve handling of the vehicle, and prevent blowouts.