Updated on 02.02.12

Air Up All of Your Tires (32/365)

Trent Hamm

Every weekday, I drive my daughter to preschool. It’s a nice routine, one that gives me a chance to spend some time with her. I make breakfast for her, make sure she’s adequately dressed for the weather, brush her beautiful long hair, and then we’re off to her preschool.

Along the path from home to preschool is a gas station. That station has the lowest gas prices within about a ten mile radius, so it’s the one I tend to use regularly.

Right next to the gas station is a free air pump, which I use about once a month or so. After I fill up, I drive over to the air pump, pull out my air gauge, check the pressure in each tire, and fill it up to the maximum recommended pressure as suggested in my car’s manual (see – there’s that car manual mentioned again).

Quite often, I’ll stop there before dropping off my daughter. She’ll get out of the vehicle with me, talk to me while I’m airing up the tires (she doesn’t quite have the finger strength to actually air them up, though we’ve tried), and often she’ll help me pull the air tube around to the proper position so that I can air up each tire.

It’s a bit of father-daughter bonding, sure, but it’s also saving me some money and subtly teaching her about a really valuable tip for auto maintenance.

Air Up All of Your Tires (32/365)

I actually learned about this tip the hard way, too.

I used to just get my oil changed at a full-service oil change place that would air up your tires for you each time. I always felt that was good enough.

In 2006, though, I started getting really into measuring my vehicle’s fuel economy and figuring out ways to reduce it. I got my oil changed on a very hot day late in that summer, and by early December I was due for another oil change.

On a very cold morning, one where I intended to actually get my oil changed and my tires inflated that evening after work, I started to pull out of my driveway when one of my tires went “pop.”

This caused me to spend most of an hour getting the spare tire on, which meant I was a bit late for work.

That evening, when I stopped by the oil change place, they noted that the spare tire was on the vehicle. They noted that the air pressure on all of my tires was almost dangerously low. They also looked at the other tire that was sitting in the back and told me that it was fine and that likely it had been pushed off by bumping into a curb or something.

That’s one way that airing up your tires can save you money and time, but that’s just one.

The biggest reason to do it is that adequately aired tires save on your gas mileage. It’s pretty clear-cut, actually.

Every psi that any one of your tires is below the recommended maximum costs you 1/8% of your fuel efficiency. So, if all of your tires are 4 psi below the recommended maximum, your fuel efficiency goes down 2%. If they’re 6 below, you lose 3%.

Let’s say your tires are running 6 psi below the maximum. That’s a 3% reduction in your fuel efficiency. Your 25 mpg car goes down to 24.25. Over just 1,000 miles, that means your car is using 1.2 gallons more in fuel than if you had maximized your tires’ air pressure. That’s $4 gone, right there.

If it takes you 5 minutes to air up your tires, that simple move is saving you money at a rate of $48 per hour of effort. That’s well worth it.

All you need is to keep a tire gauge in your glove compartment and know what the maximum PSI is for your automobile (it’s in your manual). Fill your tires up with air once every month or two – it’ll just take you five minutes. Doing so will keep your tires at the maximum recommended pressure, maximize your fuel efficiency, and keep your tires on the rims (although that only happens if you neglect it for too long).

This post is part of a yearlong series called “365 Ways to Live Cheap (Revisited),” in which I’m revisiting the entries from my book “365 Ways to Live Cheap,” which is available at Amazon and at bookstores everywhere. Images courtesy of Brittany Lynne Photography, the proprietor of which is my “photography intern” for this project.

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  1. Sara says:

    .125% * 4 = .5% … I’m confused.

  2. Misha says:

    It’s per PSI, per tire. 4 PSI short for each of four tires would be .125 * 16. Which is 2.

    I don’t know if his claim is accurate – citation needed, much? – but this is the math we’ve been given to work with.

  3. Tracy says:

    I would actually say that the *biggest* reason to keep your tire’s properly inflated is safety, and the biggest financial reason is to prevent wearing down the tread and having to replace them early.

    New tires cost a heck of a lot more than the $4/1000 miles … you’d have to drive 100,000 to make it even close to equivalent (at which point Trent would be thinking of trading in his car)

  4. Raya says:

    #1 Sara:

    0.125*4 = 0.6, but I think Trent wanted to round it up to a half per cent (0.5%).

    Kids learn not by words, but by example. And it really sticks. For me, that’s the best part of Trent’s story.

    And of course there is a safety issue if your tires are not properly pumped. Everyone should take good care of their cars – if not for yourselfs, then for the others on the road. If you blow a tire while going fast, you not only put your life in danger but also the lives of everyone else on the road (or close to it).

  5. Julia says:

    I’m not sure filling up to the maximum is always a good idea.

    You need more air in your tires if your vehicle is heavily loaded. Having less gives you better traction. Maxing out your tire pressure when your car is light will decrease traction and make the ride a little bumpy.

    Maybe shoot for being in the middle of the top half during summer. But be careful in hot weather. You never want to exceed to maximum air pressure and air pressure increases when it’s hot outside.

    Most people I’ve talked to (in Anchorage) keep their tires in the lower half during the winter. Traction is more important than gas mileage (an accident will cost you far more than the extra gas).

  6. AnnJo says:

    Besides decreased fuel economy, under-inflated tires wear out faster and have to be replaced more often.

  7. Andy says:

    Also, if you don’t feel like dragging out your manual from your probably overcrowded glove box, most cars have the recommended PSI given on a sticker on the inside of the driver’s door jamb (you see it when the door is open).

  8. Johanna says:

    Nice to see a picture with a person in it.

  9. Raya says:

    #6 Julia:

    I agree, pumping them to the max is dangerous. By the way, if you have a bike taking care of its tires yourself is good prep for when you own a car – same principles.

  10. Gretchen says:

    Again, “If it takes you 5 minutes to air up your tires, that simple move is saving you money at a rate of $48 per hour of effort” is just not true.

  11. Misha says:

    Raya @ #4 – Uh, no. .125 * 4 is .5. You can prove this easily for yourself using a calculator.

  12. jim says:

    “You can improve your gas mileage by up to 3.3 percent by keeping your tires inflated to the proper pressure. Under-inflated tires can lower gas mileage by 0.3 percent for every 1 psi drop in pressure of all four tires. Properly inflated tires are safer and last longer.

    The proper tire pressure for your vehicle is usually found on a sticker in the driver’s side door jamb or the glove box and in your owner’s manual. Do not use the maximum pressure printed on the tire’s sidewall..”

    : source FuelEconomy dot Gov

  13. Jane says:

    It’s going to be a long year.

  14. Mister E says:

    This one’s not bad.

  15. David says:

    True, the picture has a person in it – but there is also a Craftsman pump in it. Should not this be objected to on grounds of sexism?

    Moreover, although one can verify that .125 * 4 = .5 by using a calculator, one cannot prove it thereby. To see it without electronic aid, one might consider the equivalent problem of multiplying one hundred and twenty five by four: 100 * 4 = 400; 25 * 4 = 100; 400 + 100 = 500; .125 * 4 = .500. But a proof that 125 * 4 = 500 would need to begin thus:


    Addition is the function + : N × N → N (written in the usual infix notation, mapping elements of N to other elements of N), defined recursively as:

    a + 0 = a
    a + S(b) = S(a + b)

    where S is the successor function.

    For example

    a + 1 = a + S(0) = S(a + 0) = S(a)

    The structure (N, +) is a commutative semigroup with identity element 0. (N, +) is also a cancellative magma, and thus embeddable in a group. The smallest group embedding N is the integers.


    Given addition, multiplication is the function · : N × N → N defined recursively as:

    a · 0 = 0
    a · S(b) = a + (a · b)

    Setting b equal to 0 yields the multiplicative identity:

    a · 1 = a · S(0) = a + (a · 0) = a + 0 = a

    Multiplication distributes over addition:

    a · (b + c) = (a · b) + (a · c)

    Thus (N, +, 0, ·, 1) is a commutative semi-ring.

    At this point you may wonder whether the above holds if you as a commuter do not maintain steady air pressure within the semi-ring, or whether a galvanized rubber semi-ring would melt due to the temperature of the magma inside. Respectively: it does, and it would not; but the next time someone tells you that “it’s as easy as 2 + 2 = 4”, you may care to reflect on just how easy that is.

  16. Mister E says:

    And if you enter 5318008 into a calculator and turn it upside down, you get something special!

  17. Johanna says:

    David, I understand that sexism is all one big funny joke to you. Please keep in mind that there are those of us to whom it is not.

  18. kc says:

    Yawn. Thud.

  19. Andrew says:

    Blah blah blah

  20. Alice says:

    I like this photo much better than the last few; it’s interesting to look at, in focus, and seems very connected to the post.

    @17: sexism isn’t a joke.

  21. AnnJo says:

    David, while you are keeping in mind that any reference to sexism in a humorous context, no matter how innocuous, is offensive to the New Victorians among us, please also keep in mind that it is not offensive to everyone. All of the word-play in your post was entertaining, although that in the last paragraph more so than the line that set off the thought-police.

  22. Johanna says:

    I’m not offended; I’m contemptuous.

  23. Tracy says:

    It’s not offensive, but it displays a fundamental (and puposeful) lack of understanding of sexism in the ‘joke’ – and that lack means it isn’t funny, just sad.

  24. Raya says:

    #12 Misha, #17 David

    Of course 125*4 is 500. Dunno what I was thinking. Where’s my brain at?! Will never again comment late at night when there’s math involved.

  25. AnnJo says:

    That some people would insist on expressing (and presumably having) feelings of contempt and sadness based on David’s innocuous remark is a major reason why I no longer even care to share the label of “feminist” with total strangers, even after spending a good decade in the trenches of changing laws on abortion, domestic violence and discrimination, bringing lawsuits, measurably increasing the number of women in many professions – actually doing something about real sexism. Nowadays that label seems to go with a self-righteous priggishness, usually accompanied by a total lack of any real contribution toward improving the lives of women.

  26. Johanna says:

    AnnJo, you have no idea what kind of contribution I’ve made toward improving the lives of women. You have no idea, because I haven’t mentioned it, because it’s not relevant.

  27. Paul says:

    One of the things to consider is air is usually not free. I’ve seen gas stations vary between 50 cents to $1.25 for the air pump. Most places charge $1. The cost of using a $1 airpump can easily overcome the gas savings. Here’s an example.

    Assume you have a vehicle that gets (with full air) 20 mpg for city and highway combined. Lets say you just repumped the air in the tires, but if you let them go, you will fall to 19.6 mpg (a 2% loss) in three months, and the air pressure (and mpg) changes linearly with time during those 3 months. Lets say you drove 3000 miles in 3 months, which averaged 19.8 mpg (started better, ended worse). Lets say gas cost $3.30 a gallon. You purchased 3000/19.8 = 151.5152 gallons of gas at a cost of 151.5152 * $3.30 = $500. Alternatively, lets say you kept the air up by putting air in it 6 times over the 3 months (i.e., bi-weekly). Now you purchased 3000/20 = 150 gallons, at a cost of 150*$3.30 = $495. So you saved $5 in gas over the three months by keeping your tires pumped… but you spent an extra $6 on using the air pump, so you came out $1 in the hole!

  28. Rebecca says:

    Teaching children basic vehicle maintenance is good common sense, regardless of whether they are male or female. I am so thankful my Dad taught me basic skills, like how to change a tire, put air in a tire, check fluids, change wiper blades, change oil, check fuses, etc.

    Recently, one of my coworkers said she thought one of her tires was low. I mentioned checking the air pressure with the tire gauge, and she replied “what’s that?” I explained the procedure, starting with taking the cap off the valve stem, and she countered with “what’s a valve stem?” Sadly she had never asked about these things because her father and husband always took care of it.

  29. Johanna says:

    …although, AnnJo, if it’s your view that nothing remains to be done to improve the lives of women, I’m not really sure exactly what you’re expecting women in my generation to do.

  30. AnnJo says:

    Johanna, there are approximately 3.5 billion women in the world, the majority of whom still lack many of the rights and opportunities American women have attained in the last 100 years. There’s plenty of real work to do, of far greater value than expressing your contempt of David for his harmless joke.

  31. AnnJo says:

    And you’re right, Johanna, that I don’t know what contributions you’ve made to improving the lives of women. I’m inclined to believe that, in general, people who whine mightily about getting a hangnail have never experienced passing a kidney stone or a compound fracture of the leg. But of course that’s only a generality, and there are likely many cases in which it doesn’t hold true.

  32. Johanna says:

    Is it not possible, in your world, to be concerned about two or more things simultaneously, hangnails and kidney stones alike? Before you started carrying on about the “thought police” (and seriously, how am I the thought police? All I’ve done is exactly the same thing as you’re doing here – expressing the opinion that somebody else has said something ridiculous), I’d taken all of about 20 seconds to comment on David’s unfunny joke. Hardly enough to distract me from all of this real work that I’m supposedly not doing.

  33. Kate says:

    Here’s a tip: Check the pressure when the tires are cold. Tires heat up as they drive. They take about a half hour to cool down. Or you can just check the tires first thing in the morning.
    And never fill your tires when it’s extremely cold—your valve stem might freeze in the open position and you’ll have a flat tire on your hands.

  34. AnnJo says:

    Johanna, in my world, no, if I am concerned about a kidney stone, then what I might feel about a hangnail will not rise anywhere close to “concern.”

    You and I both have a tendency to serve as grammar police – telling people when they have made a grammatical error. I have never let on whether my feelings for such people include contempt (they don’t), and I may be mistaken, but I don’t think you have either. Your service as one of the thought police is similar – you are telling people when they have traduced one of the current tribalist fads. Fine, but that such error should force you to disclose your contempt for the errant suggests you are taking the duties of the job to an extreme. Here’s the Bing definition of contempt: “attitude of utter disgust or hatred: a powerful feeling of dislike toward somebody or something considered to be worthless, inferior, or undeserving of respect.” Isn’t that a little severe for David’s supposed error?

  35. jim says:

    AnnJo, I think the “I’m not offended; I’m contemptuous.” line is just a snarky quote to use which she picked up on the internet. It would make a good t-shirt for bitter teenagers. I doubt (hope) that Johanna isn’t actually literally contemptuous.

  36. Johanna says:

    “You and I both have a tendency to serve as grammar police – telling people when they have made a grammatical error.”

    Excuse me, what? You must be confusing me with someone else.

    “Isn’t that a little severe for David’s supposed error?”

    Merriam Webster’s Collegiate Dictionary, Tenth Edition defines “error” as, among other things, “an act involving an unintentional deviation from truth or accuracy.” By that definition, I don’t believe David’s statement was an error – as the pattern of his comments lately shows, his deviation from a truthful and accurate representation of concerns about sexism is entirely intentional.

    @jim: Perhaps I should explain. When people like AnnJo project “offense” onto those who say things they disagree with, it’s a way of derailing the conversation – making it all about me and my delicate feelings, not about David’s statement. “I’m not offended; I’m contemptuous” is in response to that.

  37. David says:

    This post is in the nature of a test, to determine whether every comment I make on this thread will automatically go into moderation.

  38. AnnJo says:

    Johanna, you refer to David’s “deviation from a truthful and accurate representation of concerns about sexism.” Do you mean that no one contends that “craftsman” is sexist? If so, you are mistaken; The Handbook of Non-sexist Writing lists it as a term to avoid. Do you mean that it is exempt that judgment because it is a trademark? The Sambo Restaurant chain found that exemption of little use. Or do you mean that it is a “deviation from truth and accuracy” the way that apostasy from the one true religion is?

  39. AnnJo says:

    Jim, looks like your hope is dashed. She IS contemptuous.

  40. David says:

    People, I was not making a joke (any more than I was making a joke when I asked about “the customer is king”). In future, when I make a joke I will put “joke” and “end joke” tags around it.

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