Why Are My Tires’ Valve Stem Caps Green? The Surprising Answer Revealed!

Dear Mike,

I recently noticed that my car’s tires have green valve stem caps. I tried researching online, but couldn’t find a clear answer as to why they are green. Do they indicate a certain type of tire or have any special significance?

I appreciate any advice you can give me on this matter.

Warm regards,

Dear Shayla,

I must say, it’s refreshing to receive a question about something as simple as valve stem caps. As someone who spends most of their day covered in grease and oil, it’s a nice change of pace to talk about the aesthetics of a car.

Now, to answer your question – those green valve stem caps on your tires indicate that they have been filled with nitrogen instead of compressed air. Yes, nitrogen – the same gas we breathe in and out every day.

I know what you’re thinking – “Why on earth would anyone fill their tires with nitrogen?” Well, Shayla, there are actually a few good reasons. First of all, nitrogen maintains tire pressure better than air. You see, gases expand with heat and contract with cold. This is why your tire pressure warning light usually comes on when the temperature drops. However, tires filled with nitrogen react less to temperature swings.

Secondly, nitrogen is less prone to moisture than air. Water, whether in the form of vapor or liquid, can cause larger changes in pressure with varying temperatures and can even corrode your tire rims over time. But with nitrogen, any system that delivers pure nitrogen is also going to deliver dry nitrogen. Filling tires with nitrogen involves filling and purging several times in succession to get as much oxygen, water, and other gases out of the tire as possible, leaving you with a cleaner, more stable tire.

Finally, nitrogen-filled tires save you a small amount in fuel and tire-maintenance costs. Proper inflation pressure is key to tire safety and performance, and pure nitrogen does a better job of maintaining the right tire pressure.

However, Shayla, nitrogen is no substitute for regular tire care and maintenance. As I always say – proper tire pressure is key to tire safety and performance. That’s why you should still check your tire pressures at least once a month regardless of what’s inside.

In summary, those green valve stem caps indicate that your tires have been filled with nitrogen rather than compressed air. And while there are some benefits to using nitrogen, proper tire care and maintenance should never be overlooked. Thank you for your question, Shayla. Keep those tires properly inflated and drive safely!


Mike Urban