How to put air in your tires at a gas station

Filling your tires at a gas station takes about five minutes and one number: the pressure on the sticker inside your driver's door. Everything else is technique, and the air machines are not always friendly about it.

Before you pull up

Open the driver's door and find the tire sticker on the door jamb (some cars put it on the fuel door or in the glove box). It lists the cold pressure for the front and rear tires, which can be different. Snap a photo of it with your phone so you aren't walking back and forth.

Ignore the number molded into the tire sidewall. That's the maximum the tire can hold, often 44 or 51 PSI, and filling to it makes the ride harsh and the grip worse. Most cars want 30 to 35 PSI. Our tire pressure guide has typical numbers for SUVs, trucks, spares and bikes.

Tires are best checked cold, before you've driven more than a mile or two. If you have to drive to the air, that's fine: the reading will be a few PSI high, so fill to the sticker number and leave it.

Filling up, step by step

1. Park with the hose in reach of all four tires. Most hoses are short. Pull in so the machine sits near the middle of the car, and turn off the engine.
2. Take off all four valve caps first and put them in your pocket. Caps left on the ground are how most of them get lost.
3. Start the machine. Pay, or ask inside if the station has free air. If the machine has a digital display, set it to your door-sticker PSI now. These machines fill or let air out until the tire hits that number, then beep.
4. Press the nozzle straight onto the valve stem, firmly and in one motion. A steady hiss means it isn't seated; push harder or straighten it. On a lever-style chuck, squeeze the lever to add air.
5. Fill in short bursts on a manual machine. Add air for a few seconds, then let go and read the gauge on the hose (or use your own gauge). Repeat until you hit the number. If you go over, press the little pin in the valve with the back of the nozzle or a fingernail to let some out.
6. Do all four tires, then the spare if you can reach it. A compact spare usually needs about 60 PSI, far more than a regular tire, and it's usually low when you finally need it.
7. Put the caps back on. They keep dirt out of the valve, which is what slowly leaks air over time.

If your tire pressure light was on, it should go off after a few minutes of driving. Some cars need a reset button or a menu setting; the owner's manual will say. If it stays on, our post on what the tire light means covers the next steps.

Mistakes that waste the trip

Trusting the station gauge

Gauges on gas station hoses take a beating, and some read a few PSI off. A pencil gauge costs a few dollars and lives happily in the glove box. Use it to check the machine's work on at least one tire.

Running out the timer

Paid machines give you a few minutes, and fumbling with caps eats into it. Take the caps off before you pay and you'll get all four tires done on one round of quarters.

Letting air out of warm tires

After highway driving, a tire set to 35 PSI can read 38 or more. That's normal. Let air out to 35 and the tire will be low the next cold morning.

Filling one tire and leaving

If one tire is low and the others are fine, check it again in a day or two. A tire that keeps losing air has a leak, often a nail. Tire shops patch those quickly, and some do it for free.

Where to find free air

Wawa, Sheetz, QuikTrip, Kwik Trip and Stewart's Shops are reported to have free air at most stores, and tire shops like Discount Tire and Les Schwab will top off your tires for free during store hours. The full list, with store counts, is in which gas stations have free air. Or find free air for tires near you and filter to places open right now.

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