One of my neighbors walked down to admire the new truck last night and he was giving it the full once-over. When he looked at the tires, he said "ooooh...nigrogen...fancy". I didn't know what he was talking about, but he told me that the green valve caps with the N on them meant that the previous owner aired them up with nitrogen. He said that he fills his Corvette tires with nitrogen to avoid expansion and contraction from temperature changes. He told me about the shop where he goes and said that he pays $10 PER TIRE!!!
Tipping somebody ten bucks to fill your tires is a nice luxury, but paying $60 to air up all my tires is insane.
I assume I can mix regular old air with the nitrogen that may or may not already be in there.