A tire condition monitoring apparatus includes a tire-based sensor configured to sense tire operating conditions and transmit a tire condition signal including the sensed tire operating conditions. The apparatus also includes a vehicle-based controller configured to receive the tire condition signal and monitor the tire operating conditions. At least one of the sensor and the controller are configured to determine that a tire pressure adjustment condition exists in response to determining, based on the sensed operating conditions, that a predetermined change in the number of moles of air in the tire has taken place.