oneHundred80, your absolutely right with the numbers and observation. There is a tire store three miles away that fills both my cars free. My Lexus came with nitrogen therefore I started using it in the Xfire also. If I had to pay each time I would discontinue usage. There are some that swear by it but I really don't notice any difference. Maintaining tire pressures is the key to tire life.

Ku95, maybe you should consider a future in aviation!