Dear Car Talk:
Love your column and read it every week.
My son’s car has tires inflated with nitrogen. I’m curious about the pros and cons of that option. I hadn’t heard of this before and wonder if it is going to become commonplace.
Also, is there a big cost differential vs. air inflation? — Gregory
I don’t want to go so far as to call this a scam, Gregory, because scam is a very strong word. But it’s really close. So, let’s go with “unnecessary upsell.”
There are some tire shops these days that are charging people to fill their tires with nitrogen rather than “air.” But keep in mind, air is 80% nitrogen.
Now, they cite some reasonable sounding arguments for why you might want to use 100% nitrogen rather than 80% nitrogen and 20% oxygen — known as air. For instance, they say if your car catches fire and your tire explodes, nitrogen — an inert gas —won’t feed the fire. What they fail to mention is that there’s an infinite amount of oxygen all around the tires, in the air. So that’s nonsense.
They’ll also tell you that nitrogen-filled tires don’t change pressure as much as air-filled tires when your tires heat up and cool down. This is true, but it hardly matters. The normal range of pressure variance while driving is of no consequence to most people. If you’re driving a Boeing 777, yes. But not a Nissan Versa.
Some customers have been told that nitrogen-filled tires will leak less than air-filled tires because nitrogen molecules are larger and can’t get through the rubber as easily.
Well, very little air (or nitrogen) ever seeps through the rubber. When you have a leak, it’s usually due to a puncture, a bad valve or a rim issue. And both air and nitrogen will leak out if you have “a leak.”
And finally, one pitch for nitrogen says that it’s less likely to degrade the inside of the tire the way oxygen can. OK, fine. But what about the outside of the tire? The part that’s constantly surrounded by air that’s 20% oxygen?
So, if you add it all up, unless you’re landing a plane or driving an F1 race car, it’s hard to come up with a scenario in which it’s worth paying extra to have your tires filled with nitrogen.
Maybe try helium. Then at least you can entertain the kids at their next birthday party.
Got a question about cars? Write to Car Talk write to Ray in care of King Features, 628 Virginia Drive, Orlando, FL 32803, or email by visiting the Car Talk website at www.cartalk.com.
