Is a nitrogen tire fee worth it?

Regular air is about 78% nitrogen and 21% oxygen, says NASA. A nitrogen fill raises the share of nitrogen in your tires.

Nitrogen seeps through tire rubber more slowly than air. A 2007 report by the Government Accountability Office (GAO), Congress's watchdog agency, said studies show nitrogen keeps tire pressure longer and slows tire aging.

But researchers told the GAO that no studies had shown what nitrogen does for safety or gas mileage in normal driving. Tire researchers also said either air or nitrogen works if drivers check their tires regularly and refill them when needed.

What protects your safety, gas mileage, and tires is the right pressure. NHTSA says keeping tires properly inflated helps them last longer and saves you money on gas.

Yes. If a tire is low and you can't get nitrogen, fill it with air to the right pressure. Driving on an underinflated tire is the real risk: NHTSA says too little air can lead to a flat, a blowout, or the tread coming off. And tire researchers told the GAO that either one works when you keep the pressure right.

Adding air lowers the share of nitrogen. If your deal included free nitrogen top-offs, ask where you can get them, and get that promise in writing.

• Check all your tires, including the spare, at least once a month, says NHTSA. Check them cold, when the car hasn't been driven for at least three hours.
• Use the car maker's pressure from the label on the driver's door edge or post, or from the owner's manual. Don't use the number on the tire itself.
• Keep a gauge in the car. A pothole or a curb can drop a tire's pressure suddenly.
• Don't wait for the dashboard warning. NHTSA says tire pressure warning systems only come on when a tire is significantly underinflated.

Tire experts told the GAO that air-filled tires can lose 1 to 2 psi (pounds per square inch) a month in normal driving. A monthly check catches that before it matters.

A nitrogen fill is an add-on. The CFPB says add-ons are optional: you don't have to buy them, and if you do, the price is negotiable.

Nitrogen already in the tires doesn't mean you agreed to pay for it. FTC staff guidance says a dealer can't suggest an add-on is required when it's optional. It also can't imply that an installed option can't be removed and must be paid for, or charge for options you didn't agree to. In Rhode Island, for example, the attorney general says a dealer can't charge for a product it already applied without your OK. The charge must be in the advertised price, or you must agree to it first, knowing what it is and what it costs.

1. Ask for the nitrogen charge as its own line, with the price and what's included, like free top-offs.
2. Say you didn't ask for it. Ask the dealer to take it off, or to lower the car's price by the same amount.
3. Before you sign, check the buyer's order (the itemized sales sheet) and the loan contract. Make sure the charge is gone from both.

For a sense of price, industry officials told the GAO in 2007 that some stores swapped the air in a car's tires for nitrogen for free. Others charged $20 to $79 per vehicle.

Since October 1, 2026, California's CARS Act sets these rules for dealers:

• A dealer can't charge for nitrogen tire products or services with less than 95% nitrogen purity. The law lists them as add-ons you wouldn't benefit from.
• When a dealer writes to you about any add-on during the deal, it must say in writing, at least once, that the add-on isn't required and you can buy the car without it.
• A dealer can't mislead you about an add-on's cost, limits, or benefits.

If you're charged for nitrogen, ask for the purity in writing. See what else the CARS Act says about add-ons.