Gasoline, Groceries, and a Simple Look at the Cost of Time

Recently, my wife was in rural area of Iowa where the gas prices were significantly higher than they are near where we live. While there, the amount of gas in her tank got low, so she stopped to fill up. After looking at the price and doing a quick bit of mental math, she chose to only put two gallons of gas in the tank.

Upon returning home, she stopped at a nearby gas station that consistently has very low prices and put another nine gallons in her tank, filling it up, and saving about seven cents a gallon added – sixty three cents, total.

When she got home and told me this story, I was fairly surprised. Making an extra stop for gas just to save sixty three cents somewhat threw me.

“Why didn’t you just fill up before you left that town?” I asked her.

She shrugged her shoulders. “The gas is cheap enough here that I thought it would be worth the stop.”

Being the analytical people we both are, we decided to turn to the numbers. First, I needed some accurate data on how long it would take to fill up a tank of gas. I stopped myself to fill up my truck – with a twenty gallon tank – and the entire stop took me just shy of six minutes. If you filled up a ten gallon tank, four minutes would be a reasonable estimation for a stop.

So, calculating based on that, stopping to save seven cents a gallon on gas actually saved us money at a rate of $9.45 an hour after taxes. That’s reasonably good – better than it might seem at first glance.

But it’s actually more than that. Let’s say she normally puts ten gallons in her tank during a four minute stop. Half of that time is spent parking, getting out, setting up the pump, and then turning it off and driving away afterwards. So, she pumps in the ten gallons in two minutes – a rate of a gallon every twelve seconds or so.

Her two gallon stop thus took her a total of two minutes and twenty four seconds. Her nine gallon stop took her three minutes and forty eight seconds. Add them together and you get six minutes and twelve seconds – not eight minutes.

So, she actually only invested two and a quarter minutes in pumping twice.

If you figure based on that number, she actually saved money at a rate of $16.80 by pumping twice – plus she has an extra gallon in the tank, which means she won’t have to stop again as soon.

What’s the conclusion here? Even if it seems a bit counterintuitive on the surface, it’s often worthwhile to make an extra stop if you are completely certain you can save money with that extra stop.

I use a simple rule of thumb for this – if I’m not doing anything particularly productive with my time, I’ll often jump on board with anything that’ll earn me at least $15 an hour in savings. In her situation, that’s exactly what she did by pumping twice compared to filling up just once.

This type of analysis reasserts itself with grocery shopping. There are several grocery stores in Ankeny, Iowa. The grocery store with the best selection of the items we buy is Hy-Vee. However, the best prices on staples can usually be found at Fareway.

If we had several specialty items on our list (like a particular kind of cheese or something along those lines), we would just do all of our grocery shopping at Hy-Vee, even though we’d pay a bit more per item for our other items. The only time we would split it up into two store stops is if we had an enormous grocery list.

In truth, if you’re buying more than just a few items, the amount you save for the extra time invested is probably worth the second grocery store stop. How so? If you figure that you’re familiar with the layout of both stores, it doesn’t take too long to find a particular item – let’s say thirty seconds per item to be fair.

Let’s say I can save an average of a quarter per item buying a staple item at Fareway, but we have to stop at Hy-Vee for some specialty items.

If we stop at just Hy-Vee, we invest ten minutes in getting out of the car, finding the cart, getting into the store, checking out, getting out to the car, and putting the items in it. If we stop at Fareway, we have to do that twice – twenty minutes. A ten minute addition for stopping at Fareway. However, the time actually finding items in the store is equal and, if anything, slightly favors Fareway because the store is smaller.

Let’s say I need an hourly rate of $15 in savings to make the stop worthwhile. The extra Fareway stop eats ten minutes, so I’d actually only need to save $2.50 there to make that $15 an hour rate. If I’m saving an average of a quarter per item, if I’m buying only ten staple items, it’s worth making two separate stops for groceries.

What’s going on here? To put it simply, if you know exactly what you’re shopping for and have at least a solid idea of where you’ll find the best price on a particular item, stopping at multiple places to buy groceries or doing things like only partially gassing up actually really pay off – much more than you might think on the surface.

Most people look at a quarter and just see a quarter – no big deal. A better way to look at it is to ask yourself what it really takes to get that quarter. At some point, the effort is worth it – and if you find that level, why not just keep doing it again and again? After all, quarters really add up.

If you want to get rich, watch the pennies and the dollars will take care of themselves.

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66 thoughts on “Gasoline, Groceries, and a Simple Look at the Cost of Time

  1. sarah says:

    I love your posts about grocery shopping b/c I am from Iowa (moved away 11 years ago) and when you talk about Fareway and Hy-Vee (“Where there’s a helpful smile in every aisle!”) it reminds me of growing up!

  2. princewally says:

    The aggravation of dealing with all of the people and parking and kids going in and out of two different grocery stores kills the value in making multiple trips, at least for me.

  3. evi says:

    Wow, now THAT’s detailed math! ;-) I’ve been reading your blog for over a year now and am really enjoying it – and although I am considered the very-thrifty-one in my extended family, this tops everything! I never thought of stopping myself how long it takes to fill a tank, get into a store etc… – wow. Really interesting! – But one thing that you should take into consideration is the wear and tear on the car (assuming you are going to the stores by car) if the additional stop isn’t on your way home and you have to make a detour.
    I never do my maths that properly, usually it’s a “I have time to run by an additional store so I’ll take advantage of the savings I’ll experience there”-kind of decision.

  4. Four Pillars says:

    I’m going to have to check out your time estimates for myself. I have a hard time believing that someone can pull off the road (assuming you don’t have to go out of your way to get to a gas station), get to the pump (no waiting), pump the gas, pay, leave, get back into traffic in 2.5 minutes – I don’t care how much gas you pump!

  5. wanzman says:

    Let me start by saying this: I respect your blog.

    But I am surpised at this post. I understand it must be difficult to continue coming up with new material every day. But are we really running calculations to save $0.63 by stopping at 2 gas stations.

    Money is just as important to me as the next guy…but please, to anyone that knows me, if I am ever doing anything like this…just shoot me and put me out of my misery.

    Get a life.

  6. A.J. says:

    Four Pillars – I’m not sure where you live, but if rural Iowa is *anything* like rural Illinois, I’m pretty sure Trent and his wife aren’t worrying about traffic.

    I suppose it might be different in a bigger city, but most any rural gas station is going to be on a ‘main’ road that’s not out of the way of anyone traveling more than 10 miles or so, and they’re never going to be busy enough to have a wait.

    Maybe I just live too far from civilization, though, because out here, having to wait for more than two cars before you can pull back onto the main road through town is considered ‘heavy traffic’.

  7. Johanna says:

    You’re really close to hitting on a very interesting point here. People often think about money in ways that don’t rationally make any sense. How far out of your way would you go to pick a dollar bill up off the sidewalk? How far out of your way would you go to get a box of cereal on sale for $2 rather than at the normal price of $3 (assuming you only need and want one box)? How far out of your way would you go to buy a vacuum cleaner for $99 rather than $100? Most people, in practice, have different answers to all three of those questions, but why should they, since one dollar is one dollar? The “value of time” idea has been kind of beaten to death here lately, but it can be a good way to put questions like these into a rational perspective.

    And it’s not just time that has value, but also effort. When I lived in England, there was a store very close to my house that sold soy milk – which I use a lot – for (I think) 99 pence a carton. There was also a store in the center of town that sold it for 59 pence a carton. Time wasn’t the issue here – I’d often go to the center of town for other things. The issue was that to get home, I had to walk up a big steep hill (I didn’t have a car there either), and cartons of soy milk, like cartons of any other liquid, are heavy. So I asked myself, “If someone offered to pay me 40 pence per carton to carry soy milk up the hill, would I do it?” I decided that I wouldn’t, so I went on buying my soy milk from the store near my house. Maybe that was the wrong decision – when you’re putting a price on effort and shoulder strain rather than time, it’s harder to know where to start, but it’s harder still when you’re distracted by the thought of “saving 40%” or “paying almost twice as much.”

  8. Adam says:

    Okay. Seriously. 63 cents? I think that crosses a line from frugal to cheap; unless you really have nothing but time on your hands.

    Life is too short for me to put 2 gallons of gas in at one station and 9 gallons in a cheaper place. Fill up once and be done with it, especially if its only going to cost you a whopping 63 cents. Eesh. (yeah I know, extrapolated out to $16/hour over 40 years compounded at 9% invested in a low cost index fund will net you 80 million some day because you filled your car up with cheaper gas…)

  9. Kris says:

    The problem I have with this posts is that you try to calculate something out into an hourly wage that cannot be done hourly. When talking about swapping out a light bulb for one that uses less energy, then yes, you can say that I save $x amount per hour of using the light bulb, when when making an extra stop saves you 63 cents, you cannot calculate that out into an hourly savings. Saying that you saved $16.80 an hour is ridiculous. It’s not like you can spend the next 10 hours stopping at gas stations and save $160.80… you saved 63 cents. That’s it. Nothing more.

  10. Dan says:

    Other thoughts:

    -In winter, what’s the risk of going off the road in the snow, and needing a full tank to keep the car running for heat?

    -Don’t forget that everytime you start your car, you burn more fuel than when you just leave it idle…probably lost 30 cents with the shut off and on.

    -Time isn’t so much the issue, if you can make up the minutes lost somewhere else..for instance, go to bed 3 minutes later will have less cost than the extra 3 minute stop

    -I’ve played the gas savings game, a lot. I usually will either time my fuelings for the off days (wed, thurs) as opposed to higher days (friday, monday)…but i’ll pay the extra cost if it’s within a buck.

  11. Hope D says:

    I think the biggest way to be frugal is to have good habits. I live close to a state line. We cross the state line to go shopping every once and a while. The gas is much cheaper across the line. It is a habit to fill up the tank when I cross over or come back. It may not save me money every time with a cost time ratio, but the habit saves me money in the long run. If I had to sit down and run the numbers on $.63, I believe that would be a waste of time. My time all day is not maximized. I don’t believe all time is money. I wouldn’t sleep if I did.

  12. Alexandra says:

    I guess this is what passes for entertainment around your house – getting the calculators out and gloating over a savings of 63 cents.

    The problem with this kind of behaviour is that it does not seem like a means to an end (i.e.: you are trying to save money for a goal). Rather it appears that you are deriving all your pleasure from savings of any kind, no matter how small or inconsequential. The danger is that you become emotionally attached to money in a different way than over-spenders do. Money loses all value becuase it is the HOARDING of it that brings you pleasure, not the lifestyle that can be achieved if you earn and save the money.

    My uncle was like this – bragging all the time about his crazy little financial “wins” of 50 cents here and there, being frugal in ridiculous, time-wasting ways. At first he had purpose – it was to get out of debt, then it was to buy a house, then it was to retire early and sail around the world on a boat. After many years of extreme frugality, he is in his sixties, still working full-time with several million in the bank, and he cannot spend anything because he has lost sight of the real purpose of money. His frugality ruined everything for him. We keep telling him to relax and enjoy the rest of his life and HE CANNOT. It stresses him to spend any money on what he considers to be a luxery. His life is sad – he worked hard all his life and now he cannot enjoy the fruits of his labour.

    It just sounds like you may be heading along the same path. 63 cents just should not be that big of a deal to someone without consumer debt and doing well. Maybe you need to chill out a bit over the inconsequential “wins”.

    I found this post disturbing and sad.

  13. leslie says:

    I am curious how time factors into the gas equation for people who live in Oregon and New Jersey; where self-serve is non-existent (technically, illegal).

    I still have to invest the time to wait for the guy to come take my credit card, pump the gas, then come back and give me my receipt.

    But during this time, I can check/send work emails on my iPhone, re-organize my to-do list, pluck my eyebrows, and several other productive things while sitting in my car waiting for the gas to be pumped.

  14. Craig says:

    It makes sense sometimes, but I don’t think you need to go all the way out of your way to try to save a few cents, get what is close sometimes and save time.

  15. Chelsea says:

    I’m going to post in Trent’s defense. I think this post is less about saving money and more about entertaining oneself trying to solve a complicated problem. Both my husband and I like numbers and word/math problems, and we would have had fun trying to figure this one out, too.

  16. Amy B. says:

    I think that we all have things that we will do to save a buck, and things we won’t do. The important part of this post is that you have to periodically validate the assumptions that you use to decide if a savings is worth the extra time.

  17. Ryan says:

    I don’t think it’s fair to say you saved $16.80. You didn’t even save close to that, you saved 63 cents.

    Adam, I think you win this comment thread. “(yeah I know, extrapolated out to $16/hour over 40 years compounded at 9% invested in a low cost index fund will net you 80 million some day because you filled your car up with cheaper gas…)”

    Hilarious.

    Trent, you do a lot of frugal stuff that I agree with. CFLs, Energy Efficient Appliances, Prius (at least on the gas bill), hell, even the home made laundry detergent I can get my head around.

    But the time and energy wasted to save 63 cents blows my mind.

    I know they save a penny saved is a penny earned…but come on.

  18. Luke says:

    If there is a person in line ahead of you at the pump, then your savings drop in half.

    In hindsight it looks like good savings, but what if the cheaper gas station was closed, credit card machine was broken, shift change, or anything that would throw off the time-based calculations.

    Might as well eat the 63cents and get gas when you can.

  19. Shannon says:

    I’m sorry but this post is completely ridiculous. If you derive a joy in this kind of calculation and activity (ie this is an end by itself), then good for you, otherwise this is ridiculous.

  20. Four Pillars says:

    I think you also have to consider the time it took to determine if the saving was worthwhile. If it took you several minutes then your hourly wage just dropped in half. :)

    @AJ – I live in Toronto and I would normally have to go a little bit out of my way to get to a station. Not much, but enough to change the time factor significantly.

  21. Lise says:

    *sigh* I never understand the negative comments on posts like this. It’s simply meant to be informational. As Trent has said many places, if the information isn’t useful to you, that’s fine. There are people it will be useful to.

    That said, on a random tangent, I always enjoy hearing about the names of grocery stores in other states. It’s amazing how different they are! I’ve never even heard of Hy-Vee or Fareway. Of course, you’ve probably never heard of Hannaford or Shaw’s or Market Basket, either.

  22. Doug says:

    Is this a parody? If so, it was worth the time to read it as it’s an excellent example of the silliness in taking frugality to extremes. If it’s not a parody, well, just think of how much money I could have been making instead of reading this. Probably at least 63 cents. Overall, I like Trent’s work so I’ll give him the benefit of the doubt and just think of this as a parody.

  23. Andy says:

    If I knew I had a 100 mile round trip (25 mpg x 2 gal x 2) and not enough gas (2 gal), I would have filled up at the place that has consistently low prices BEFORE leaving town… how much $ per hour would that have saved?

  24. Dave says:

    So she spent 2 minutes and 12 seconds extra on pumping gas, instead of being home enjoying her family. how far out of the way is it to go to this gas station you normaly use?
    Now if it was a matter of filling up in your hometown or where she works, on a regular basis for a few cents that makes sense,
    They have 10 cents off gas sundays in the next town from me, I did the math, if I’m not going though there anyway it costs me more in gas to drive there and back than I save.

  25. Jeremy says:

    2 minutes and 24 seconds to make an extra stop at a different gas station? I think you left out a few key assumptions:

    1) You don’t have to make a single turn off of your route home to hit up the second gas station.
    2) The second gas station is on the right hand side of the street so you can pull in and out easily without making any left turns.
    3) There isn’t anyone in front of you forcing you to wait for a pump.
    4) The credit card machine functions twice as fast as any I’ve ever used.
    5) There are never any other unforeseen problems.

  26. lurker carl says:

    The 63 cents saved on one tank can be extrapolated over the course of one year rather than broken down into an hourly rate. For instance, 100 tanks of gas purchased over the course of one year would save $63.00 per year. Not $16.80 per hour! This post makes sense when the appropriate units of measurement are applied.

    This post disects a common situation and confuses it with some mathematical gymnastics and statistical overkill. Spending 63 cents less for a tank of gasoline is not something that should be assigned an hourly rate.

    The crux of this story is needing a consumable product but the price nearby is higher than at home. So she buys only enough to last and gets a full quantity at the cheaper price. And she doesn’t go out of her way for the lower price – consuming $1.00 to save 63 cents is counter productive, to say the least.

  27. Lloyd says:

    First off, I’m glad I could read this article. But I can’t agree at all with the premise.

    It’s just plain faulty (and kind of deceptive) to say you’re saving at over $15/hour. Why does the rate matter? You are NOT saving 15 dollars in an hour. You ARE saving 63 cents at a cost of 2.5 minutes, but you still only have 63 cents. That’s it.

    Also, what if you try this next time and you hit a traffic jam? Or the credit card machine doesn’t work? Or you have a hard time trying to find parking spot? Now your savings are being TAKEN from you at a rate of $15/hour or more. That’s why it’s not worth it to do these exercises. It’s almost like trying to time the stock market.

  28. Lee says:

    LOL Trent. I love it.

    I’m not certain your math is accurate, but 10/10 for the post regardless.

    I suppose the next question has to be how much is your wife’s time worth? i.e. if Bill Gates dropped a $100 bill, it’d be cheaper for him to keep walking than go back and pick it up.

    If you factor in the value of your time (rather than sheer cost), did she still make a saving?

  29. brad says:

    can we get an update on john and his campground?

  30. Johanna says:

    You know, usually I am much more befuddled by the “HOW DARE YOU CRITICIZE TRENT!” comments than I am by the critical comments themselves, but I’m surprised by the negative reaction to this one. Maybe it’s because I don’t have a car, so I don’t have to take it personally that stopping for gas in Trent’s town is apparently a lot more straightforward than it is in my town.

    True, the gas savings aren’t scalable. But so what? A lot of the “dollars per hour” rates mentioned for various things aren’t scalable. Making laundry detergent isn’t scalable, since you can’t save more on laundry detergent than you were spending on it in the first place. Fixing the toilet isn’t scalable, since you can’t fix the toilet more often than it breaks. Arguing with the manager at Target to honor your raincheck isn’t scalable. And so forth.

    I do agree with the folks that point out that if there’s any significant possibility of being delayed during the second gas stop, it’s not worth it to make two stops. And yeah, the post would have been more complete if Trent had mentioned some of the uncertainties that could come into play. But I don’t think his analysis is meant to apply to every gas station in every situation – it’s meant to apply to this particular situation and this particular gas station, which Trent’s wife knew (presumably) she’d be driving right past, where she knew she wouldn’t have to go out of her way or deal with extra traffic or wait for a pump. And I’ve spent enough time in rural areas that I can believe that she would know all those things.

  31. Scott says:

    This post is a good example of how statistics and math can be used to pretty much “prove” any outcome you want.

    As many have said, attaching an hourly rate to this just doesn’t compute in my book. MAybe collective yearly savings, but not an hourly rate.

    However, I do appreciate the gist of the post – take conventional wisdom and what your first reaction is, and consider if it would be better another way.

  32. Matt says:

    To those saying “yeeesh fill er up and forget about it, it’s just .63 cents.” Think about if you’ve ever driven out of your way to find the gas station that is 3 or 5 cents cheaper per gallon? In reality you only save about the same amount between that and a higher price station as what is in this post. I’m willing to bet though that most of you are willing to drive that extra time to get to the cheaper staion so what Trent’s wife did in my mind is really no different. She took some extra time to get to the cheaper gas. Trent is simply just explaining that she was mathmatically justified in doing it.

  33. J says:

    These calculations prove …. that you can make the numbers add up to anything you want when you pile on the numbers and tweak assumptions.

    Number of posts in a given time period is one way to measure the success of your blog …. as are number of hits, number of comments and so on. While there have been some interesting and insightful posts over the years, these “I’m going to add up some stuff to show what my time is worth when I save $.50 or $1.00 over 10 years” are really tiresome and the “gains” can easily be wiped out by a rounding error.

  34. Marsha says:

    As a single woman, I’d gladly pay extra for gasoline to make sure I don’t run out, especially if driving in rural areas.

  35. Marsha says:

    Oops, to clarify my post above: as a single woman who drives by herself a lot, I’d gladly pay extra for gasoline to make sure I don’t run out, esp if driving in rural areas. :P

  36. Kelly says:

    @Lise….I’ve heard of Market Basket ;)

    In my area of the country(NE Ohio/NW PA), we’ve got Giant Eagle(Pittsburgh based grocery chain), Wegmans(Rochester NY grocery chain), Tops, and Quality Market. I shop primarily at Giant Eagle as it’s the closest one to me with an AWESOME $4 prescription program/Free antibiotics program.

  37. Penny says:

    Gee whiz, if the post is about time vs. what it’s worth, I’m back again to the arguement of “if your time is so precious, why are you wasting time reading all the way through, and THEN posting? Really, now?

    Anyway, I don’t run the numbers for gas, because I guess I’m just not that motivated for gas, as I live four miles from my job. I’d bike, but I’m terrified of being struck by a car, plus, being a teacher and having to lug papers makes it difficult.

    However, I do enjoy doing calculations about the money I save on food. My post today involved the price of dried beans, derived from the price of a twenty five pound bag and the weight of a cup of them. Waste of time, maybe for some, but plenty of folks tell me my bread making is a waste of time too. The same ones who have lengthy conversations about American Idol… To each their own.

    It’s all about what is important to you and what applies in your life.

  38. Bill says:

    Wow, I’m kinda surprised this isn’t another post about how smart it was to finance your Prius.

  39. greg says:

    Sometimes, you just want to stop twice during a long trip, to stretch your legs, get some fresh air, exchange a few friendly words – and if you can save 36 cents by making the second stop at the cheaper gas station, that comes as an extra benefit. Other times, you just want to get home before the kids go to sleep, and would not think about stopping twice. In the second situation, your time has a much higher opportunity cost, and in the first it does not. As you see, the value of your time varies from one situation to the next.
    And then, you did not count the time it takes to make the time vs. money calculation each time you need to take a decision which is worth a few pennies. For you, Trent, this is work and gives you something to write about. For the rest of us, it could be a good rule-of-thumb to choose the cheaper option whenever we can — unless we have a strong feeling that it would be a serious waste of time and effort.

  40. Suzie says:

    Or you could ditch the car altogether, and walk everywhere! You save the entire price of the gasoline that way, not to mention the initial cost of the car, the services, the new parts…

    Or bike. Of course, you’d have to adjust your life-style a bit, but adjusting your lifestyle is what it’s all about.

    And you’d save on gym memberships, wii-fit games, and other ‘exercise-enhancers’.

  41. Ramona says:

    “Lies, damn lies, and statistics” We can justify everything.

    The post was less interesting than the comments – thanks Trent for the controversy.

  42. Dennis Robert says:

    63 cents is pretty much nothing but 63 cents once a week for a year is … $32. I dunno, I guess ideally go for the cheapest gas you can most of the time, but if you need gas just get it.

  43. Kelly says:

    @Suzie..walking everywhere is just not practical when one has a 30 mile commute to work. Especially when one lives in the snowbelt along the shores of Lake Erie.

  44. Rob says:

    Heres how I calculate time. I did this today: I get out at 6 pm to go get my son. I need gas before I get him, because I need to take him to school tommorow morningwhich is 40 min away. Instead of stopping to get gas on the way to get him, and deal with the nimrod in line, who is taking about 3 min to get his act together, then waiting to pull out of the gas station because of a line of cars, and because I want to get him as soon as possible back home…………..I got gas at lunch regardless of the price. I’m leaving to get him in 20 min knowing I have a full tank of gas, not stopping at different gas stations to get a good price.

    The day someone stops at a gas station or goes to a grocery store and can actually go right in and out, without having to deal with the dummies in line, you let me know.

  45. almost there says:

    While I agree that this post shows how to save money getting cheaper gas, like others I don’t think you can assign an hourly dollar value to the savings unless that time would have been directly used earning that $16+ per hour wage. I commute 100 miles RT so know about stopping in less expensive locations. I track each gallon purchased on quicken and be able to determine at the end of the year how much I spent on gas for all my vehicles and the average cost per gallon, and cost per mile. Just as a study, I never do anything with the data. Say, isn’t it about time for an update on how much Trent saved over the year on TP? :)

  46. kristine says:

    Wow. What heated responses! I routinely fill up just enough to last me till I naturally pass one of the cheaper stations about 20 minutes away, and then fill up. So 2 gallon/9 gallon is routine for me. But it is in the normal course of things.

    Here in NY, The gas station near me (full serve) is charging 3.40 today, and in a less affluent community, where I go to BJs, the cost is 2.65. The savings is much bigger.

    Even so, I would not turn it into a dollar per hour, I turn things into time worked, based on my current job position. If I save 7 bucks or more on a tank of gas, would I prefer to work an equivalent amount of time for the convenient route? Even if that is not a possibility, the thought process makes me evaluate how hi a priority that convenience is. Besides, I can do that calculation in my head.

    I have an amusement- do you ever calculate in the time spent calculating? I consider it entertainment, but most people don’t.

  47. Todd says:

    I like the saying “Watch your pennies and the dollars will watch out for themselves.” However, as sayings go, it’s also possible to be “Penny-wise but Pound-foolish.” Personally, I’d prefer to skip the occasional big treat to make up for not having to count pennies like this for routine purchases.

    I agree with others that the comments on this one have been fun to read.

  48. John says:

    Again, your math is ridiculous, and your hourly cost analysis is even worse. Your wife did the right thing by only purchasing the amount of gas required to get home to where the gas prices are cheaper. Unless you are actually “on the clock” at a paying job you aren’t making money, so by saving $.63 or whatever the number is, you are still actually saving that amount.

  49. Jacinta says:

    I also thought this post was a little ridiculous, but I think Trent is correct in how to calculate savings. When we extrapolate something into an hourly rate, it’s not to suggest that we’ve saved an hour’s worth. Instead it allows you to apply a value to a given amount of time. This then gives us a comparison. It’s better to do things which save us money at a high hourly rate (even if they mostly just save us cents) than it is to do things which save us money at a low hourly rate.

    So Trent’s wife spent about 3:48 filling up the second time and saved 63 cents (although Trent explains that this is only an additional 2:25 from filling up to full in the first stop). I know I would take longer, even if I didn’t have to wait, but let’s pretend that’s valid. The only way to properly determine whether 63 cents is a good saving for 2:25 is to extrapolate it into an amount of time that makes more sense. To do this we solve:

    (60 seconds/time spent * cents saved) = (60/2.25 * 63) = 1679.58 cents or $16.80/hour.

    This doesn’t mean you can keep up this activity over a longer period of time and actually save $16.80, it just means that this savings was at a rate of $16.80. It is still only 63 cents saved today, and only $32.76 if you did this weekly for a year.

    Consider a movie. In Australia, it costs $18 for an adult to see a movie at the cinema. Most movies run for about 2 hours, so we’re paying $9/hour. On Tuesdays, some cinemas sell tickets for $10 per adult. This means the same movie now only costs $5/hour, for a saving of $4/hour. If Trent’s scenario is correct, it’s better value for time spent to fill up twice than it is to see a movie on a Tuesday, so long as you were going to see that movie anyway (in either case you’re still down at least $10 from your entertainment budget). This doesn’t mean that seeing movies on Tuesday is bad, it just allows you to compare the comparative savings.

    If Trent’s wife spent an extra 5:00 filling up that second time (which is still much less than I would spend) then the hourly rate of savings would be $7.56. Perhaps that would still be a good deal for some people, but not for me.

  50. Jonathan says:

    Many of the comments to this article show that what works in one area of the country might not work as well in another area. If rural Iowa is anything like rural Kentucky, then being able to stop and get a couple gallons of gas in 2 1/2 minutes should be no problem. There are a couple of key things that make that possible.

    First, most of the gas stations here are located right off of the main rural roads. There is no going out of your way to stop, you’re passing by anyway. Second, whether the station is on the right or left side of the road is normally not as issue, as there is little traffic on the rural roads. At most you might have to wait for one or two oncoming cars to pass, taking an extra 10 or 20 seconds maybe. Third, rural gas stations here are not normally very busy. It is very rare that I have to wait in line to pump my gas. If there is a wait, and I can make it to another station I’ll often just wait, since most likely there will not be a wait there. Last, if using a credit/debit card to pay at the pump, there is no waiting in line or dealing with the other customers. For this reason, I will not stop at a station without pay at the pump unless I have no other options.

    The arguments that it isn’t possible to stop and get 2 gallons of gas in 2 1/2 minutes are probably accurate in certain areas. If you live in a city, have to go out of your way or wait for a traffic light to turn to cross the road, that takes more time. If the station is usually busy and you have to wait in line to use a pump, that takes more time. If you don’t use pay at the pump, and go into the store to pay that takes more time, especially if there is a line at the counter or the cashier is not efficient.

    As far as I’m concerned, this article makes perfect sense. My initial reaction was that some of negative comments are from people who just don’t get it, but then I realized that most likely those posters just live in areas with very different variables, in which case Trent’s calculations would not be accurate.

  51. Dave says:

    I guess if one wants to go far enough with the math, you could figure the wieght of the extra gas, and fighre the milage savings, and just keep just enough gas for each trip, it’s all just a matter of how far to take it.

  52. Amanda says:

    This is silly. Rural or urban—the math isn’t realistic. I think many folks have learned enough from life & this blog to move on. Let’s all stop obsessing folks. This post convinced me of that. I hope this blog sticks around in an archive form to help those new to being a bit thrifty, but I think the topics are getting quite thin. (JMHO.) Going overboard in thriftiness can lead to a miserable life—I have personal, very sad proof of that in my family like another poster in these comments. Keep it normal & enjoy the life that your sane thriftiness affords you. Thanks for a good blog Trent, it was very enjoyable.

  53. Matt says:

    In addition, I no longer have to think to myself “am I making the right decision to buy a little now to get to the cheap gas later?”. Thanks to this post I don’t have to run the numbers myself, I know that it is the correct decision. Trent’s time in doing the calculation is saving me the time of doing it on the fly.

  54. Evita says:

    Well…. this post is the perfect example of the obsessive nickel and diming that turn people right off frugality!
    I don’t dispute the actions leading to this minuscule saving (I could have done the same!) but all these calculations to equate it with a hourly wage are just plain silly…… it does not relate to real life in any way.
    Silly posts like this one also turn me off from the blog, unfortunately…….

  55. dsz says:

    I’m not on board with the hourly wage calcs, particularly since any small change in the actual time can skew the value one way or another-but-I do the same thing simply because I get cheezed off if I spend more than necessary due to my own inattention and I know for a fact I will waste more time in a day than it takes for that second fill-up.
    I make a point of checking gas prices on my way to a local destination and then fill up at the cheapest station on the way home. I also will shop at up to four grocery stores in a given week depending on the sales. I may only buy one or two items at each store so maybe the ‘hourly rate’ isn’t the best (never crossed my mind, to be truthful) but the extra 15 minutes or so I spend per store isn’t eating into my otherwise productive time anyway so it’s worth it to me. Two of the stores are within 2 miles of my house and the other two are near other places I frequent so there’s no real extra cost for getting there.
    36 Kelly-I’m sort of in your area and we have Giant Eagle, Buehler’s, Acme and Wal-Mart (all our Tops markets closed). I do most of my staple shopping at Wal-Mart, meat at Sam’s, veggies at the year-round farmer’s market and loss leaders at the rest. Giant Eagle’s prices are obscene (around here, anyway) and Wal-Mart has the $4 prescription deal as well.

  56. Lou says:

    What no one has mentioned is the fact that Trent writes this blog for a living, so the time he took to do the calculations was just part of his job, as it would not be for most of us.

    Re: extrapolating the wage per hour idea. I’m retired, so i like the idea that i could be “paid” so much an hour for being thrifty. I like that formulation!

  57. Hannah says:

    You recently wrote another post about how you have to add your own time into the equation, because you could have been doing something so productive.Yet you didn’t do that here. Stop trying to quantify things like this. It doesn’t work!

  58. Nancy says:

    Is it common for people in Iowa to ask for “x” amount of gallons of gas? Do you have to give them the exact amount, or do they get pissed if they see you handing them a $10?

    Who would want to be in “rural Iowa” with only two gallons of gas in their tank? What if there was some event/emergency that prevented you from getting home (or to the cheap station) before the two gallons ran out? Then how much time and $$$ would have been saved? More than 63 cents, I’m sure.

    My father, “Mr. Safety”, would be appalled.

    And I agree with Eva – Another article that my non-frugal peers will read and throw at me.

    Is this all really part of some weird experiment that you’re not telling us about?

    :o-)

  59. joan says:

    I’ve been known for squeezing a dime and getting at least 15 cents worth out of it, but even this seems not really worth it for me.

  60. joan says:

    By the way, you get better gas milage out of a full tank of gas than you do from an empty or near empty one. Check it out if you don’t believe it. I try to never let my gas tank get below the half mark, because I check to see how many miles a gallon I get every time I fill the tank. So, if you get 1 or more miles per gallon more out of a tank of gas; how does that calculate with only putting two gallons in the tank.

  61. Jonathan says:

    @Joan (#60), can you explain your logic regarding getting better mileage on a full tank of gas? That seems counter intuitive since the car will weight slightly more with more fuel in the tank.

  62. almost there says:

    I think Joan #60 is being fooled by her gas gauge. My car shows that I drive more miles the first 1/2 tank of gas but that is due to the gas gage not being calibrated, miles divided by the actual gas replaced up to the automatic stop when filling up gives a true mpg every time.

  63. Adam says:

    Perhaps not better mpg for a full tank, but starting and stopping the car and shutting off the engine and turning it back on again use more gas than just driving straight home. That needs to be factored into the money equation too ;-)

    While I don’t agree with this post, I do want to state that I enjoy Trent’s blog immensely, and this is definitely an entry I will share with my sarcastic friends. The jokes they will make should be funny indeed.

  64. Thank you for the detailed analysis. I’m relieved to find that my multiple shopping stops likely add up to savings after all!

  65. Dottie says:

    If this were me and I forgot to fill up with enough gas for a long trip before I left I think I would have just filled up at the more expensive station far from home, considered the 63 cents a sunk cost and chalked it up to experience. As a frugal person and an accountant by trade I am all into numbers, however I have never been able to routinely use the cost per hour for every financial decision I make. I usually just use it for repetitive long term choices. However, as a frugal person it would have gone against the grain to fill up with gas I new I could get cheaper. For 63 cents I don’t think there is a right or wrong answer, just what fits your lifestlye best and makes you feel like you made a good decision.

  66. Louise says:

    I don’t understand why people freak out over this. This is like washing plastic zip lock bags; it saves you a few pennies here and there, but if you do it consistently, along with similar cost-saving measures, you really do save money! If someone feels it’s worth the few seconds or minutes it takes, then you should do it. If you make a habit of doing things like this over the year, you could easily save a decent chunk of change. I’m sure I save at least $400-$500/year by doing little things that just take a moment or two. Maybe that doesn’t seem like a lot to you, but that money can be invested in something else that saves you money, like a sewing machine, a home freezer, or similar item.

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