If You See a Green Cap on Your Tire Valve, This Is What It Means

The benefits of inflating car and truck tires with nitrogen gas is trending, but the technology isn’t necessarily new. Since the 1980s, the FAA has mandated nitrogen be used in aircraft tires. Nitrogen is also commonly used in race cars and heavy-duty mining equipment. But is it worth the extra $20-plus for putting it in your personal vehicle? Here’s how to decide.

What Are the Green Caps on Tires For?

Green caps on tire valve stems signify that the tire is filled with nitrogen instead of regular air.

Nitrogen vs. Ordinary Air-Filled Tires Pros and Cons

Nitrogen-Filled Tires

Pros:

• Less moisture buildup
• More stable tire pressure (less affected by temperature changes)
• Less pressure loss over time

Cons

• More expensive
• Not always readily available
• Marginal benefits for everyday drivers

Ordinary Air- Filled Tires

Pros

• Less expensive
• Widely available

Cons

• Pressure fluctuations
• Moisture collection, which can corrode tire beads and harm tire pressure sensors
• Potentially more frequent filling

Nitrogen vs. Ordinary Air-Filled Tires: Which Is Better?

It depends. Nitrogen has benefits, but “for most everyday driving, air is all that is needed,” says Paul Knoll of AmericanMuscle. “However, if the driver seeks more consistent tire pressure and potentially longer tire life with fewer maintenance intervals, nitrogen would be beneficial.”

Family Handyman master technician Bob Lacivita agrees. “It can’t hurt your tires,” he says. “For most drivers, regular compressed air is fine. However, if you live in climates where there are large temperature differences, do a lot of highway driving in warm conditions, or can get nitrogen for a few dollars at local tire store, it would be a good idea.”

Either way, get a good tire pressure gauge and check the tire pressure regularly.

FAQs

How long does nitrogen last in tires?

Several months, on average. Tires filled with nitrogen tend to maintain their pressure longer than those filled with ordinary air.

How much does it cost to refill nitrogen tires?

It ranges from around $5 to $10 per tire. Knoll says some service centers also offer unlimited refills for a one-time cost.

Where do you get nitrogen for tires?

Nitrogen for tires is available at many tire shops and automotive service centers.

Is it okay to mix nitrogen and air in tires?

Yes. It won’t do any harm to mix nitrogen with regular air in your tires, though that may degrade or eliminate the benefits of the nitrogen.

About the Experts

• Bob Lacivita was an award-winning General Motors master technician for 27 years and has been an ASE master technician since 1978. For 25 years, he also worked as an automotive technical educator and administrator. Today he writes about DIY car repairs and vehicle maintenance for Family Handyman, Reader’s Digest and other outlets.
• Paul Knoll is a dedicated car and truck enthusiast with a lifelong passion for vehicles and sharing his knowledge with the automotive community. He has worked his way up at AmericanMuscle.com for more than a decade and is currently marketing director.