What Do Green Caps On Tires Mean? (Explained)

When you see green caps on tire valve stems, it means such tires are nitrogen filled rather than regular air.

So, if you are going to refill such tires, ensure they are also filled with nitrogen to keep enjoying the benefits of nitrogen in tires.

Nitrogen in tires is not a new concept as it has been around since the 1960s, but it is something yet to be popular mostly because of the cost and availability.

We want to understand why someone would want to use nitrogen over regular air and many other aspects of nitrogen-filled tires below. Keep reading.

Why Nitrogen-Filled Tires?

Just as the name suggests, such tires will be filled with nitrogen rather than regular air. This has several benefits, especially for people who might not have the time to keep checking their tire pressure all the time.

Nitrogen has larger molecules meaning that the tire would lose less nitrogen as compared to when you have filled the tire with air. So, you can be assured to have the tires inflated for longer.

Some might wonder, can mixing air and nitrogen affect the performance of the tires? That is not something that should worry you. This is because the mixture does not affect the tires, but only reduces the nitrogen effectiveness in the tire.

One important thing to put in mind is that you should always use the right tire pressure just as you would when filling with regular air.

So, what are some of the benefits of filling the tires with nitrogen? Here are some that you should know.

  • Improved gas mileage: Of course, when you have properly inflated tires, you are likely to experience better gas mileage even if it is regular air. However, nitrogen helps maintain inflation at the right level for longer.
  • Improved tire longevity: If the tire pressure is maintained for longer, it means you are always driving at the right inflation. This always ensures your tires last longer.
  • Better handling: Another reason for nitrogen-filled tires is that you can have better handling always as the tires are always filled to the right level.
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Types of Nitrogen Tires

One thing to note about nitrogen is that it can be filled in all common tires. There are no special nitrogen tires or regular air tires. The difference is that nitrogen tires will have a green cap to help someone know the difference.

The common tire types you can inflate with nitrogen include;

1. Summer tires

The summer tires are made to work well in dry and wet conditions. You should find them working great during the summer months, hence the name. So long as the conditions are warm and dry, they should be good enough.

Using nitrogen in the summer tires is highly recommended if you want to maintain consistent tire pressure in case there is a change in temperature drastically. Remember, cold or hot weather also affects your tires.

Here is a video on how temperature affects tire pressure

YouTube video

2. Snow tires

Snow or winter tires contain special treads and rubber to help improve traction in winter. Some even come with metal studs key for improving traction too. So, you will always have an easier time driving through snow or ice with such tires.

The tires could also use nitrogen since it can be useful in such cold conditions too. You will find that you are losing less tire pressure when you fill the tire with nitrogen compared to air. Yes, the temperature variations could lead to loss of tire pressure.

3. All-seasons tires

The all-seasons tires are made to be a safe bet for areas experiencing different weather conditions. The good thing about such tires is that you do not need to replace them more often during each season. This can save you time and money.

Filling these tires with nitrogen can help maintain the correct tire pressure regardless of the season. Even with the temperature and season changes, you do not need to worry that you have lost air pressure.

4. Performance tires

You can get performance tires on luxury vehicles generally. They are commonly wide and have a low profile.

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They can be good for looks and also increases performance. You can fill them with nitrogen to also experience more performance without having to refill them more often.

5. Offroad tires

Yes, even off-road tires can use nitrogen. This is because it is possible you want more performance off-road without worrying about refiling the tires. Just make sure the tire pressure is right for the conditions you are about to drive through.

What to Consider Before Filling Tires with Nitrogen

Are you considering buying and filling tires with nitrogen? Here are a few things to consider before filling tires with nitrogen.

The budget

You might not always get a place to fill your tires with nitrogen and if you get one, expect to pay for it. Most of the time, you may pay an average of $5 to $10 to fill a tire with nitrogen.

That is a cost you would not incur when you used regular air. So, if you have a budget for it, then there is no problem paying for the refills.

Current fill in the tires

In case the tires are already filled with nitrogen, you would then have to continue adding nitrogen to the tires to experience all the benefits of nitrogen.

If you decide to use regular air for a tire containing nitrogen, then expect to reduce the nitrogen benefits, but the tire would not be damaged.

For those who want to put nitrogen in their tires but have regular air already, then it is advisable to deflate the tires to remove air first before refilling with nitrogen.

Ease of access to nitrogen stations

Now that you know how much nitrogen would be good for your tires, you would then consider ease of access or availability of nitrogen stations. This is for those who do not like mixing nitrogen with regular air.

In case you have to travel, research more about the common stations that would offer nitrogen-filling services.

Why Use Nitrogen in Tires Rather than Regular Air

Many people are used to filling their tires with compressed air and now they know there is the option of using nitrogen. So, before you can switch to nitrogen, it is best to understand how the two compare. That is what we discuss below.

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Cost and ease of access

Compressed air is readily available at most tire centers or even a gas station in your neighborhood. However, the same cannot be said for nitrogen. You can see that someone would think that it is easier to refill with compressed air than nitrogen.

That is not all as the cost is also another huge factor. Nitrogen filling costs around $5 to $7 per tire. Some installers can charge up to $180 for the whole process of changing from compressed air to nitrogen-filled tires.

Most tire installers do not charge for compressed air. That is a big win for compressed air.

Winner: Air

Maintaining tire pressure

Maintaining your tire pressure is quite important if you want the tires to wear evenly. However, you might notice that there is a difference between the two in terms of which can be held in the tire for longer.

Consumer Reports did a study to understand if you would lose the tire pressure at the same rate when filled with nitrogen. The study found that the rate at which the tires would lose pressure was slower than when filled with tire pressure.

The tires lost an average of 2.2 PSI per year while those filled with compressed air lost 3.5PSI per year.

You can see that it is not a big difference, but it can be enough to sway someone to think about nitrogen-filled tires.

Winner: Nitrogen

Fuel economy

The EPA estimates that you experience a drop of 0.3% in case you lose 1 PSI in all four tires. This is because a drop in PSI leaves you with increased rolling resistance which in turn reduces gas mileage.

ExxonMobil in 2008 found that filling the tires with nitrogen will not change the rolling resistance. This shows that filling tires with nitrogen does not always guarantee better gas mileage. It could be slightly better because tires hold nitrogen for longer than air, but the difference is not too much.

Winner: Tie

Preventing wheel corrosion and long-term tire aging

Compressed air contains 78% nitrogen combined with 21% oxygen. The oxygen in the air may potentially lead to corrosion of the wheel and premature tire aging.

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It is not the worst corrosion, but it can potentially lead to faster wear and tear of the tires. Of course, most tires now have paint protection applied, which can help with preventing corrosion.

Nitrogen is an inert gas that does not support moisture. The nitrogen used in the tires is 93 to 95% pure nitrogen. As you can see nitrogen would be good to help reduce the possibility of wheel corrosion and long-term tire aging.

Some experts have however claimed that under normal driving conditions, the difference is not the biggest, but using nitrogen is highly recommended if you can afford it.

Winner: Nitrogen

  Nitrogen Normal Air
Components Has only nitrogen Contains some nitrogen and oxygen plus other gases
Cost High Low
Tire consistency High Medium
Safety High Medium
Fuel efficiency High Medium

Here is a video comparison with more details

YouTube video

How to Refill Nitrogen in Tires

Refilling tires with nitrogen is not hard. You only need to find a local dealer or gas station that has the facilities to make the process smooth.

Normally, the dealer removes the regular air in the tires and then refills them using nitrogen several times to help remove moisture and oxygen that might be still in the tire.

Depending on the dealer, some might require a membership purchase before giving you this service.

Of course, you have to look at the availability of such dealers before deciding to switch to nitrogen-filled tires. The last thing you want is to be stranded with no tire pressure.

It is possible at times you find yourself in situations where you need more tire pressure, but you do not have access to a nitrogen filling station. In such a case, we recommend that you can use compressed air, no problem at all.

It is best to have the car inflated at the right air pressure rather than driving at low tire pressure. Again, mixing nitrogen and compressed air does not harm the tire.

Here is a video explaining the nitrogen tire-filling process

YouTube video

Summary: Should You Use Nitrogen in Tires?

Nitrogen can be a good alternative to using compressed air in your tires. It can potentially improve tire aging, prevent wheel rusting, boosting gas mileage, among other benefits.

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If these benefits work for you, then consider using nitrogen in your tires. You should definitely consider the availability of nitrogen filling stations before using them exclusively in your tires.

Are you intrigued to give it a try? If so, consider looking for local dealers in nitrogen tire filling in your area to enjoy all these benefits.


Can you put regular air in green cap tires?

Yes. There is no problem doing so, only that you will not enjoy the same benefits as you did when you had filled the tires with nitrogen.

How often should you check nitrogen-filled tires?

You can always check weekly like you would with tires filled with normal compressed air. As for refilling, once every two to three months should be fine.

Can you mix nitrogen with air in tires?

Some people mix the two hoping to get the benefits of the two. However, you will not get all the benefits listed for nitrogen. So, it is best to stick to either nitrogen or just regular air.

Is nitrogen readily available at gas stations?

Only a few gas stations will have a nitrogen-filling service. This means you might find it hard to keep refiling the tires with nitrogen unless you plan in advance.

When was nitrogen first used in tires?

The first time this unique concept got put into practice was in 1963 by Olin Mott. Of course, you can come across many dealerships claiming to have done the same, but Mott was among the known pioneers of using nitrogen in tires.

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