2003 Subaru Outback Owner's Manual - Page 412

HB0382 Driving even a short distance warms up the tires and increases the tire pressures. Also, the tire pressures are affected by the ambient temperature. It is best to check tire pressure outdoors before driving the vehicle. When a tire becomes warm, the air inside it expands, causing the tire pressure to increase. Be careful not to mistakenly release air from a warm tire to reduce its pressure. NOTE D The air pressure in a tire increases by approximately 4.3 psi (30 kPa, 0.3 kg/cm2) when the tire becomes warm. D The tires are considered cold when the vehicle has been parked for at least three hours or has been driven less than one mile (1.6 km). WARNING Do not let air out of warm tires to adjust pressure. Doing so will result in low tire pressure. Incorrect tire pressures detract from controllability and ride comfort, and they cause the tires to wear abnormally. 11-40