regular air or nitorgen

hi all,
i just noticed my 2010 cx-9 GT have green caps on all four tire valve, assuming they are all filled with nitrogen. what happen when i need air for my tire? is ok to fill it with regular air and mix with nitrogen.

thanks
simon

Regular air is fine.

You already have 80% of nitrogen in the air

The whole point of using pure nitrogen, according to my research from the web, is about oxidation of
valve and rubber. Oxidation on the valves causes slow leak. Oxidation of rubbers causes blow-outs.
The latter is a severe issue for tires that get re-treaded over and over again such as those on 18-wheelers.
(that is why one of the two on each side each axle cannot be a retreaded one)
Not really an issue on common vehicles like our CX9.
Oxidation on the valves is a minor issue if you check your tires every couple of months.
With TPMS, the sensors will inform you.

Anyway, it is not about 80% nitrogen in the air we breath. It is about the few percent of oxigen that cause oxidation. Besides, pure nitrogen contains much less moisture than the air we pump into the tires ourselves.

The bottom line is that I use normal air to fill tires. I don't mind people (like Costco) put in nitrogen for me as long
as it is FREE....

Nitrogen or Air!!!! Well, don't care much either one. As long I regularly check for the pressure, and keep it as recommended, it should be fine. As Ceric said, FREEEEEEEEEEE is always welcome...