Change of seasons and temperature are times to check tire pressure. Tires are permeable and on average lose a pound of air a month. Some tires have special liner coatings that reduce air loss. When we shift from summer to winter temperature changes can drop tire pressure as much as 8 lbs or 25% leaving more tire on the ground and increase in surface friction causing tire wear and excess fuel consumption. It is the number one reason for MPG loss. So remember to check tire pressure regularly.