Sorry if this has been discussed before, but…
Is there any reason NOT to switch to nitrogen to fill my tires?
Fill away. This will keep your tires from becoming under-inflated at 30,000 feet.
Not if your interested in spending money unnecessarily. It will not harm tires, only your wallet. There is no real world benefit, and you’ll wind up paying again for more pump ups if they lose pressure.
Regular air is already 77% nitrogen. The air in the tires is regular air, and “filling” the tires with pure nitrogen only means adding nitrogen until the pressure is increased from room ambient to whatever the tire spec is, say 30psi. The air that’s in your tires never gets purged out. The net result is probably that your tires end up with 80% nitrogen instead of 77%.
And it really doesn’t matter. Nitrogen has absolutely no advantage over air (77% nitrogen, 22% oxygen, 1% argon + miscellaneous) for the average daily driver. Places that tell you otherwise ar using it as a sales gimmick.
Only if it costs you money. As others pointed out,there are no significant advantages or disadvantages.
I’m sure you meant to say only if it’s free.
If the nitrogen is free, no. If you have to pay for it, yes.
Air is mostly nitrogen anyway (about 78%), so there’s not much to be gained with pure nitrogen, especially if you pay extra for it.
I’m sticking with air.
Thanks, all. I can get it free with service at my Honda dealer, and theoretically topping off is free too, but from what you’re saying, it really won’t make that much of a difference–especially since I don’t plan to drive at 30,000 feet (!).
If it costs you money don’t switch to nitrogen.
It’s not that it won’t make much of a difference. It’s that it won’t make any difference.
Here is the argument for putting nitrogen into tires: http://www.getnitrogen.org/why/index.php What does seem most plausible is that “normal” air contains water vapor which can freeze at altitude in aircraft tires.
We used to love the nitrogen cart when we filled up the aircraft tires. We didn’t need ear defenders! No starter, no dead battery, no fuel tank to check or fill; we were happy. We love opening valves. We didn’t like it when the tanks were low, but they lasted long enough and it was somebody else’s job to change them or fill them. It was heavy but three people would hardly have trouble pushing it. We hated the hydraulic fluid pump cart. It was tiny and hard to find if you forgot where you left it. You looked silly towing that little box. Nitrogen is good; it’s one of my favorite gases. It does little for the average car tire. Don’t worry about beating last weeks subject to death. I had one day with whether or not a Barracuda would beat a Mustang and it was worse than any subject discussed or procussed here.
I know the new Nissan GT-R comes from the factory with nitrogen filled tires
Not losing air so quickly is a decent reason to use nitrogen, even though there’s little risk of the water vapor in my tires freezing at altitude. 
But apparently there is some difference; e.g., that the tires won’t have to be filled as often, right? And if the initial fill-up and subsequent top-offs are free, having nitrogen in my tires certainly can’t hurt them, right?
I really do appreciate all these replies. Thank you, all.
If you have alloy wheels, which are prone to leaking if moisture pits out the sealing bead, then nitrogen in the tires is what you want to use. Nitrogen contains no moisture.
The son works for an automotive service center, and it’s his job to repair alloy wheels that leak. He says as soon as he breaks the bead of the tire off the wheel, and that white cloud of aluminum oxide comes rushing out, he knows that the wheel has oxidized at the bead and pitting of the wheel bead has probably occured. Or the wheel has oxidized where it’s now porous and the air leaks thru the wheel casting itself.
So if you have alloy wheels, he’s a firm believer of putting nitrogen in the tires. Because he sees what a little moisture can do to an alloy wheel.
Tester
Nitrogen makes no practical difference in losing pressure. CR tested it, found like a 1 psi difference over a year. Completely inconsequential.
And a reason not to do it is if you ever let your pressure drop because you can’t find a nitrogen place. That’s why I don’t like those nitrogen caps on tires, likely results in underinflated tires.