Nitrogen vs air in tires: is nitrogen worth it?

Jump to: What nitrogen inflation is · Nitrogen vs air at a glance · What the tests found · Pressure loss estimator · Topping up with air · Green valve caps · TPMS note · Is it worth paying for?

What is nitrogen tire inflation?

Shops that offer nitrogen run compressed air through a generator that strips out most of the oxygen and moisture, then fill your tires with what is left: mostly nitrogen. The U.S. Tire Manufacturers Association (USTMA) describes it as basically nothing more than dry air with the oxygen removed, and notes that ordinary air already contains about 78 percent nitrogen. So a nitrogen fill is not a different substance in your tires; it is a higher concentration of the gas that is already the main ingredient.

Nitrogen has real uses in demanding jobs. USTMA says aircraft, mining and heavy commercial equipment use it to reduce fire risk if brakes or wheels overheat, and racing teams use dry nitrogen to cut pressure swings caused by moisture. For normal passenger and light truck service, USTMA says nitrogen inflation is not necessary, though it is permissible.

Nitrogen vs air at a glance

Question	Regular air	Nitrogen fill
What is in the tire	About 78% nitrogen, 21% oxygen, 1% other gases, plus some water vapor (Consumer Reports, NHTSA)	Mostly nitrogen with little oxygen or moisture; Consumer Reports used 95% purity in its test
Slow pressure loss through the rubber	Yes. Air filled tires lost 3.5 psi on average over one year in the Consumer Reports test	A little slower. Nitrogen filled tires lost 2.2 psi on average in the same test; NHTSA’s lab found new nitrogen tires lost pressure at about two thirds the rate of air
Moisture	Can carry some water vapor	Dry, which is why racing teams use it for consistent pressures (USTMA)
Rolling resistance and fuel economy	Same as nitrogen when kept at the correct pressure	No direct effect on lab rolling resistance (NHTSA); any gain comes only from staying closer to the right pressure
Still need monthly checks?	Yes	Yes. USTMA and Consumer Reports both stress nitrogen is not a replacement for regular pressure checks
Cost	Usually free or low cost	Often $5 or more per tire at dealers and tire shops (Consumer Reports); some shops include it free with new tires

What the tests actually found

• Consumer Reports, one year test. Consumer Reports filled one tire of each of 31 all season tire models with air and one with 95 percent nitrogen, set both to 30 psi, left them outdoors for a year and rechecked them. Air filled tires lost an average of 3.5 psi and nitrogen filled tires 2.2 psi, a 1.3 psi difference over the whole year. Its tire program manager stresses that both kinds lose pressure, so owners still need to check routinely.
• NHTSA laboratory study (DOT HS 811 094). In a 90 day static test, new tires inflated with nitrogen lost pressure at roughly two thirds the rate of new tires inflated with air, with similar results under load on a roadwheel. Nitrogen had no direct effect on lab rolling resistance. NHTSA also found that air filled tires in everyday service drift toward more nitrogen on their own: oxygen escapes faster, and oxygen in 76 in service tires had dropped from 21 percent to an average of 15 percent after about three years. That means nitrogen’s advantage shrinks over time.
• Tire aging. NHTSA’s oven aging test suggested oxygen speeds internal aging, but every tire filled with either nitrogen or normal air passed the durability test. Consumer Reports’ reading is that this is not a practical concern for most drivers, who wear tires out long before oxidation becomes the problem. For age limits see our how long do tires last guide.
• Other leaks matter more. USTMA points out that punctures, the bead where the tire meets the rim, the valve and the wheel itself can all leak and may cancel out any benefit from nitrogen. Temperature matters too: pressure drops as it gets colder, whatever is inside. See our cold weather tire pressure section.

Industry view, clearly labeled: the Get Nitrogen Institute, an organization that promotes nitrogen inflation to drivers, truckers and fleets, says nitrogen improves handling, fuel efficiency and tire life through better pressure retention and cooler running tires. Those claims come from an advocacy group; the independent findings above show the measurable benefit for passenger tires is small.

Air vs nitrogen pressure loss estimator

See roughly how much pressure a tire might lose through the rubber alone if you never topped it up. This is an estimate that spreads Consumer Reports’ one year average losses (air 3.5 psi, nitrogen 2.2 psi, starting from 30 psi) evenly across the months. Real tires also lose air from temperature swings, punctures, beads and valves, so your actual numbers will differ. It runs in your browser and stores nothing.

Placard cold pressure (psi)

Months without a top up

Estimate only, scaled in proportion to your pressure from one published test. It is not a prediction for your tires. Always set pressure to the value on your door placard, measured cold.

Can you mix nitrogen and air?

Yes. USTMA says nitrogen and air can be mixed in any proportion, and that nitrogen filled tires can and should have air added whenever nitrogen is not readily available. Driving on low tires to avoid "diluting" the nitrogen is the real mistake: USTMA warns that relying on nitrogen to reduce pressure checks can lead to underinflated driving and premature tire failure. Consumer Reports agrees there is no harm in adding regular air; it just reduces the nitrogen benefit you paid for.

What do green valve caps mean?

Green valve stem caps are the common signal that a shop or dealer filled the tires with nitrogen, and Consumer Reports notes some cars are sold with them already fitted. The cap itself does nothing special; it is a reminder. If you bought a car with green caps, you can keep topping up with nitrogen where it is convenient or simply use air. Either way, keep a cap on each valve to keep dirt and moisture out of the valve core.

Nitrogen and your TPMS light

Nitrogen does not change how your tire pressure monitoring system works. NHTSA says TPMS only warns when a tire is significantly underinflated and is not a substitute for a monthly check with an accurate gauge. A slower leak from nitrogen just means the light may take a little longer to come on; it does not mean the tire is at the right pressure. Our TPMS warning light guide explains what the solid and flashing lights mean.

Is nitrogen worth paying for?

• If it is free with new tires: fine to accept. It will not hurt anything.
• If it costs extra: most drivers are better off spending the money on a good tire gauge. Consumer Reports concludes consumers would save money by using regular air and checking monthly.
• Either way: follow NHTSA’s advice to check all tires, including the spare, at least once a month when cold, meaning the car has not been driven for at least three hours, and set them to the placard value, not the number on the sidewall. Our cold tire pressure guide walks through it.

Informational only, not professional or safety advice. Your tire maker, vehicle manual and a trained tire technician take priority over this page.