Recently the manager at my local oil and lube shop came in and apologized for putting air in my tires. A bit confused, I laughed and told him that was, of course, okay. Later I realized that the green caps on my Jeep’s tires were the source of confusion.
For the manager, the green valve stem caps meaning was clear, the tires were filled with nitrogen and not just regular air. He assumed I had paid up to $30 per tire to fill them with nitrogen and his service attendant had ruined that. Actually, the caps were just extras that I had laying around the garage.
That said, the manager was right, green caps indicate tires are filled with nitrogen.
Why use Nitrogen? Let’s find out.
A Quick Overview of the Science
The air we breathe, and put in tires, contains 78% nitrogen and 21% oxygen with the remaining 1% made up of other gasses such as argon and carbon dioxide.
By going to a nitrogen dealer, drivers are able to boost nitrogen levels in their tires to 93% – 95%. This is considered “pure.”
According to Consumer Reports, nitrogen tires lose on average 2.2 psi of pressure over the course of a year versus 3.5 psi for air filled tires. As discussed below, that difference has several positive benefits for tires.
Why Use Nitrogen in Tires?
Pros of using nitrogen include:
- Tires lose pressure more slowly
- Consistent and correct air pressure means better fuel efficiency
- Mildly better handling
- Nitrogen is less flammable (while good, this is not that big of a deal)
- Less wear on tires due to consistent pressure and lack of water vapor inside of tires.
The biggest con, of course, is the cost. Most people get their tires inflated for free when getting an oil change. For interim fill ups, most service stations and car washes have coin operated compressors that cost roughly a dollar.
Converting to nitrogen requires completely deflating tires and refilling with nitrogen. Sources vary but reported costs range from $7 – $10 per tire up to $30 depending on location. Additional costs are incurred for “topping off” the pressure each year. Pro tip: Costco members receive free nitrogen, but this is very rare at other stores.
Is Nitrogen Worth It?
The short answer is “probably not” unless you have a high-end Porsche, Corvette, Nissan GT-R or similar personal supercar.
Car tires are easy to inflate at home, which means people are more likely to keep them at an optimal psi. Also, using the figures above, air is likely to be conservatively $50 – $75 cheaper between initial inflation and routine top offs.
Where to Buy Valve Stem Caps?
If you do have nitrogen filled tires, I definitely recommend using green valve stem caps. Otherwise you run the risk of having service attendants putting regular air in your tires. That can get costly in a hurry.
My favorites are the chrome plated brass caps with the N2 green symbol.
These are very stylish and much more durable than plastic caps. They also stand out limiting the risk of attendants not noticing them.
If you want stylish valve stem caps but don’t have nitrogen in your tires, use colors other than green. Several great color options are available and are very affordable.
The “green valve stem cap meaning” is that your tires are inflated with nitrogen instead of regular air. If you have a performance car or a big budget, using nitrogen definitely has benefits. It’s just a little costly.
Otherwise, use regular air and routinely monitor your tire pressure. It’s much cheaper and you don’t lost that much performance.