Beware The "MPG Illusion" When Comparing Fuel Efficiency

Sure, switching from a gas guzzler to a highly efficient (and probably much smaller) car is best for the environment, but it’s not a realistic solution for large families or people who can’t afford it. But don’t let the fact that you can’t buy a 40 mpg car turn you off of a trade up in efficiency anyway. A couple of economists have pointed out that “using ‘miles per gallon’ as a measure of fuel efficiency leads people to undervalue the benefits of replacing the most inefficient automobiles.” Their point: if you’re driving a gas guzzler, even a small improvement in fuel efficiency can generate significant savings.

Gillis calculated that at $4 a gallon, over 10,000 miles, an improvement from 12 mpg to 13 mpg would save $256. For the owner of a 33 mpg car to save that much, mileage would have to go up to 40 mpg, he said.

Here’s how it works.

A couple drives a 25 mpg sedan. They trade it for a 50 mpg hybrid, a 25 mpg improvement.

A family with mom, dad and three kids has a 10 mpg SUV to haul everyone around. They trade it for a 20 mpg station wagon, a 10 mpg improvement.

Sounds like the couple did better, at least in miles per gallon.

But lets look at gallons per miles.

At 25 mpg the couple burned 400 gallons over a year and their new 50 mpg hybrid cuts that to 200 gallons. They save 200 gallons.

At 10 mpg the family’s SUV burns 1,000 gallons of gas a year. At 20 mpg the station wagon burns 500 gallons — they save 500 gallons, much better than the couple.

Obviously you stand to save the most with the most efficient car. In the above example, though, you’re spending so much on gas for that big vehicle that cutting your consumption in half can save you $2,000 a year. It’s worth keeping this in mind if you’ve been assuming it’s cheaper to stick with your old 10 mpg vehicle, or if you’re car shopping on a limited budget and tempted to disregard modest fuel efficiency ratings.

“Seeking better gas mileage? Think backwards” [CNN]
“The MPG Illusion” (subscribers only) [Science]
(Photo: Getty)


Edit Your Comment

  1. trance3303 says:

    this might be the most informative post in a long while

  2. chilled says:

    voodo math..

  3. Coder4Life says:

    This article is completely crap. I am sorry.

    They both save 50% from what they are used to spending.

  4. sleze69 says:

    Forget miles/gallon. Go with cost/distance traveled. That way you can fairly add diesel fuel into the equation.

  5. Skiffer says:

    Hooray for basic math!!!

    CNN, you so smart!

  6. Chris Walters says:

    @Coder4Life: The point is, the person with the 10 mpg vehicle who can’t trade up to a 40 mpg vehicle might take a look at a 20 mpg vehicle and think it’s not worth the trouble because it’s still considered “inefficient.” You know how people are with off-the-cuff math, reasoning, and so on.

    Another way of putting it is that each person should figure out how much the target vehicle will save him, not just compare mpg rankings and disregard the less efficient choices that are actually within his budget.

  7. statnut says:

    @Coder4Life: Yeah really.

  8. Farquar says:

    @Skiffer: I am so smart. S M R T.

  9. Skiffer says:

    @Farquar: Me fail English?!? That’s umpossible!

    Let’s turn this thread into nothing but Simpsons quotes…

  10. mavrick67 says:

    @Coder4Life: 50% of $1000 is $500 and 50% of $600 is $300, how is that crap?
    . . . unless you work for Safeway where a dozen is 12

  11. CRNewsom says:

    @Coder4Life: You are correct and so very wrong at the same time. If a person saves 50% over what they are used to spending, and they are used to spending a fortune, the return is much better. The rate of return is different, but my wallet doesn’t measure rates very well. It does, however, measure extra cash well.

  12. SaveMeJeebus says:

    The internet? That thing still around?

  13. PunditGuy says:

    The sedan to hybrid family spends $800 a year on fuel @ $4 a gallon. The SUV to wagon family spends $2000 a year.

    So, SUV to hybrid saves nearly $5000 after just over four years. Unless you’re a man named Brady, WTF do you need all that SUV space for anyway?

  14. PunditGuy says:

    Sorry, that’s wagon to hybrid.

  15. rbb says:

    This is just a sad commentary on the poor math skills of the average American. This information ($$$ is already present on every new vehicle sticker and from the epa website.

    Furthermore, the article does not even mention that any gains in fuel efficiency may be lost by the cost of trading in avehicle, the higher cost of a new vehicle, higher insurance costs, etc. Sometimes, it is cheaper to stay with the guzzler…

  16. milqtost says:

    @PunditGuy: Meanwhile buying the new Hybrid only cost the family $30000 (plus interest if they don’t pay cash)! Big savings for all!

  17. @SaveMeJeebus: We call it Interslice.

  18. kc2idf says:

    I suspect this is why Europeans (except the English, who still use MPG, as far as I know) measure fuel economy in litres per 100km, effectively pre-inverting the number.

    @sleze69: Depends on your goal. On this board, miles/$ or km/$ is a perfectly appropriate metric. Others may consider instead miles/BTU or km/J (in which Diesel fares about the same as gasoline). From a deeply environmental perspective, you may want to go even further and go to miles/bbl crude, in order to get down to the bottom of how much of the black stuff actually needs to come out of the ground and go into the air to cover your travel needs.

  19. jpx72x says:

    @Coder4Life: Sorry, but my paycheck doesn’t come in percentages, and they don’t sell gas that way, either.

  20. seanSF says:

    Two things, all math aside: 1) We can all (ok, most) do with smaller cars, and 2) When do we get the wagon that can easily carry the three kids and gets 50 miles to the gallon??

  21. legwork says:

    Hostile posters already? Are you guys claiming the math is wrong, or just that it’s an optimistic approach?

    To me the OP is reminding people to view the decision from multiple perspectives. i.e. While our family can’t give up the Expedition for a Metro, we could switch to something that would save enough coin to make it worthwhile.

    Results come all the easier when shoppers stop looking at a new Prius as the glory ride and instead concentrate on value.

    Something I’m not sure has been mentioned here is reducing insurance costs for a second vehicle by suspending coverage when it isn’t used. We only activate our SUV insurance once a month when we need to pull a trailer.

  22. kingmanic says:

    @milqtost: Which is only $4000 more then the non hybrid of the same model… I don’t think the hybrid versions are 30k more then the non hybrid ones. Unless your buying a maybach?

    The only ones considering the trade are:

    1- Those shopping for a new vehicle
    2- Those saddled with a expensive to run vehicle
    3- Those willing to put money into an ideological belief (ecology).

  23. justbychance says:


    I’d like to introduce you to the new Jetta diesel Sportwagen. The kids would have to be small, but it’s a wagon, should get 50+ MPG.

  24. Charred says:

    False savings FTW.

  25. Charred says:

    I eat comments. Om nom nom.

  26. PølάrβǽЯ says:

    @PunditGuy: “Unless you’re a man named Brady, WTF do you need all that SUV space for anyway? “

    It’s not just space, it’s capability. I drive a small 4×4 SUV (Ford Explorer, small compared to most Chevy SUVs) even though I only have two kids. Why? I go places with it that a car or minivan could never go, and not just out of recreation. I live in a rural, mountainous area; four wheel drive and high ground clearance are often required just for friends’ driveways. Also, I often pull a Bayliner 175, a car trailer or a utility trailer.

    Believe it or not, some people actually have good use for their SUVs.

  27. battra92 says:

    @PunditGuy: Unless you’re a man named Brady, WTF do you need all that SUV space for anyway?

    One word: Wheelchairs. My grandmother really could only fit in our old GMC Jimmy which my dad kept until it was really unsafe. He got 15mpg in it but could haul the wheelchair that would not fit in my trunk or any wagon he saw. Hell, it barely fit in the Jimmy!

    He got a 20-22 mpg Tacoma and while not great, it’s not bad either.

    SUVs make sense when they are full. A full 20mpg SUV seating 5 is just as efficient a people mover as a 2 seat 50mpg vehicle. Heck, even a so called Smart Car is actually pretty dumb when you do the math (two people in a truck beats one in Smart and possibly a Prius. Of course, five in a Prius beats an SUV anyday but for some larger families they just don’t make sense.

    Where I’m seeing inefficiency of cars are the people who drive them and how they are used. I also see plenty of full SUVs and empty Priuses.

    When I go to work I see tons of SUVs without anyone in them but the driver so I suggested to my HR dept that we start some sort of company carpooling and now I carpool 2 days a week or more going a mere mile out of my way and he chips in a few bucks a week so we both get a bargain.

  28. jchabotte says:

    Who cares how much you are spending on gas? What matters is the cost of ownership of that car for the 100,000 miles..

    My wife’s car will be paid off in Sept. She had a payment of $300/month.

    Now.. she doesn’t drive around enough for the increased mileage of a new vehicle to offset the cost of a new car payment by saving $300 a month in gas.

    plus insurance on a new car.

    People who complain about the cost of gasoline but then spend money on a new car need their heads examined.

  29. ClayS says:

    Exactly right, and in fact the man named Brady doesn’t need an SUV necessarily. If his issue is seating capacity he lives in the city, a van would probably be a better choice.

  30. Gopher bond says:

    @jchabotte: I wish I could convince my wife of this. When I was young and stupid, I had a car payment. I busted my ass to pay it off and not having a car payment makes a HUGE difference on the family budget. My wife like to trade in after 3 years and get a new car. So yeah, she will forever be paying off a car.

    She complains about the price of gas. I don’t.

  31. @Coder4Life:

    This article is completely crap. I am sorry.

    They both save 50% from what they are used to spending.

    I don’t spend percents, I spend dollars. If they both save 50%, but the second person saves $250 more, I’d rather be the second person.

  32. bohemian says:

    Dump the SUV and buy a used high mpg car FTW!

    We have cut about 75% of our gas consumption by buying a used high mpg car, using it for the majority of our driving by sharing the car back and forth and then cutting how much we drive in total.

    We didn’t realize exactly how much driving we were doing until we started tracking it. The savings in gas by driving the car vs. the SUV pays the car payments.

  33. @SaveMeJeebus:

    The internet? That thing still around?

    Man, it’s all around you right now! Watch out!

  34. jstonemo says:

    My 1999 Chevy Silverado gets 15 mpg and is paid off. I spend about $85/week in fuel.

    I could go buy a “fuel efficient” car that gets 30 mpg for around $400 a month and still have to buy fuel.

    $340/mo. gas

    “fuel efficient” car:
    $400/mo payment +
    $170/mo gas =

    Total monthly expenditures are what matters in your budget.

  35. howie_in_az says:

    @bohemian: Or get a high mpg car as the commuter car; chances are people aren’t taking their kids and boats and whatever with them all the time, so why drive the SUV all the time (or at all, but that’s besides the point)? Get an inexpensive commuter car that you drive to/from work, and keep the guzzler in the garage until there’s a family outing that warrants using it.

    Or wait for the sub-$25k 100-mile range electric car that better come rsn.

  36. milqtost says:

    @kingmanic: Except there isn’t a non-hybrid version of the Prius. Which seems to be what everyone holds up as the example here (I’m pretty sure the Tahoe Hybrid doesn’t get 50mpg). But what I really meant was that not everyone has the money to go buy a new car just to save $5000 on gas over 4 years.

  37. nedzeppelin says:

    this is retarded….

    miles per gallon and gallons per mile are practically the same thing.

    1/mpg = gpm. it’s stupid.

    i guess they just mean, for stupid people who can’t do conversions, this might make a car look more efficient.

    a car that gets 25mpg gets 1/25 gpm. woooooooo simple math.

  38. stevejust says:

    @milqtost: I bought my brand new honda civic hybrid for $18,600 in 2004. The alleged costs of new hybrids are greatly over exaggerated.

    Moreover, it’s equipped comprable to a $15,000 Civic LX. So I paid $3,600 more for the hybrid. But then I got the $2,000 tax credit in 2004. So I paid $1,600 more for the Civic. Doesn’t take too long to save that premium here in Los Angeles where gas is $4.69 a gallon.

  39. balthisar says:

    The LX is the stripped down Civic (you know, since you mentioned equipment — I owned an Si and an EX, but prefer Lincolns now). Also, Priuses and most other hybrids now have waiting lists and people paying OVER sticker. Tax credits are gone. It’d be nice if everyone could afford/acquire a hybrid, but it’s not just economically feasible for everyone. My own car is paid for — there’s not even a used car that would be worth the trouble of changing into just for a 30%-50% increase in mileage (gotta consider comfort, too).

  40. dondiego87 says:

    To all the commenters doubting whether this story makes any sense… Try actually doing the math. Let’s see how many gallons of gas are used in an average year (15,000 miles)…

    25 mpg: 15,000 miles * (1 gallon / 25 miles) = 600 gallons
    50 mpg: 15,000 miles * (1 gallon / 50 miles) = 300 gallons
    10 mpg: 15,000 miles * (1 gallon / 10 miles) = 1500 gallons
    20 mpg: 15,000 miles * (1 gallon / 20 miles) = 750 gallons

    As you can see, the difference over 15,000 miles between 25 and 50 mpg is only 300 gallons, as compared with the difference between 10 mpg and 20 mpg of 750 gallons. The people going from SUV to station wagon saved 2.5x as much gas as the people going from the sedan to the hybrid sedan!

    I heard this on the NPR: Environment podcast this morning. The interviewee said that a more effective way to visualize fuel savings is to think in terms of “gallons per mile” (which does not equal mpg, as a commenter upstream suggested, except when mpg = 1).

    25 mpg = 0.04 gpm
    50 mpg = 0.02 gpm
    10 mpg = 0.1 gpm
    20 mpg = 0.05 gpm

    Here, you can see that the difference between the sedan and the hybrid is only 0.02 gpm, as compared with the difference of 0.05 between the SUV and station wagon. (Again, a 2.5x difference!) This is a much easier calculation than converting mpg to gal/year, and would be made even easier if the government required this figure to be displayed on cars as is apparently common in Europe.

    (The only problem I have with this whole idea is that going from a 10 mpg SUV to a 20 mpg station wagon still isn’t as good as going from a 10 mpg SUV to a 50 mpg hybrid… But I guess some people really need [or want] the space.)

  41. nedzeppelin says:

    you end up spending the same dollars and burning the same gas whether you consider the mpg or gpm of your new car. thinking about the statistic upside down doesn’t change the car’s fuel efficiency.

    you can do the conversions at home to get to whatever statistic you want, and the car won’t care. it will be just as fuel efficient as always.

  42. plasticredtophat says:

    @jstonemo: your forgeting insurance too…

  43. Geekybiker says:

    In the end I could care less about MPG. I care about $ per mile.

  44. unpolloloco says:

    I’d have to drive 375000 miles to justify the cost of a new prius, given my current car (17-yr-old 25mpg car with next to no resale value vs. a $30000 50mpg prius). This calculation does not count any other costs into the equation, such as insurance (would go WAY up), nor the amount of money I would be making in interest on the $30k I wouldn’t spend. At 5% interest, I could drive 9375 miles a year for essentially free, compared to if had I bought a Pruis.

  45. snoop-blog says:

    hybrids are good at hiding all those extra costs that you don’t think about because you’re only worried about mpg. what about your electric bill going up? I’ve also heard that you have to pay an extra tax in some states for owning a hybrid. those batteries? about 1200 a piece. Anyone who has ever had a battery powered device should know that there’s only so many times you can charge battery before it’s junk. I could go on if I had the time because there are more hidden costs that just what I have here, but I leave in an hour so I need to get all the blogging I can in now!

  46. B says:

    @snoop-blog: Uhhh, you don’t plug in a hybrid, at least until the Volt goes on sale. Nice try, though.

  47. ???/??? says:


    There are no plug-in hybrids in production right now. The only slated one is the Chevy Volt, which may never come out by the looks of it. The idea really of plugging it in is not to save incredible amounts of cash, but to reduce the use of foreign oil. Not to mention, you more then likely aren’t looking to plug it into your standard 110V outlet, it’s probably going to be something where you would plug it in at a station. Or possibly you have another 220V line run in your house like your washer.

    And the cost of batteries $1200 is really not something you’d probably consider as an expense on your hybrid. At most, they would have to be changed once later in the life. Compare that to the cost of changing your belts, pulleys, and alternators and the cost offset is not exactly life changing. But again, the biggest benefit of a hybrid is the reduction on foreign oils.

  48. Justafan says:

    I think you also have to consider gallons/occupant/mile. An SUV getting 10 mpg with 5 occupants utilizes 0.02 gallons to move each occupant one mile. This is equivalent to each occupant driving a 50 mpg hybrid.

    This is why buses are such efficient people movers. A bus getting 6 mpg with 30 occupants utilizes only 0.0056 gallons/occupant/mile.

    An SUV full of people can actually cancel out the smug generated by a lone driver in a Prius.

  49. B says:

    @Justafan: You realize that a hybrid can fit 5 people too, right?

  50. TechnoDestructo says:

    To the author of this article, and to every person who thinks there is anything even remotely insightful here: You are to report to your nearest middle-school for re-education. Apparently the last time didn’t take.

  51. Justafan says:

    @B: I’m just sayin’ that a SUV full of people is equivalent to “one” driver in a hybrid.

    It would take a greyhound bus full of people to cancel out the smug generated by five people in a hybrid.

  52. Corydon says:

    I’m going to be the annoying guy who points out that my bicycle gets 0 gallons per mile or ∞ miles per gallon :P

  53. Justafan says:

    This is still America. People are free to drive what they can afford to drive.

    Th point I’m trying to make is that a SUV owner who regularly keeps the seats full has no reason to hang his head in front of his hybrid owning friends. Especially if the the SUV owner can not afford a more efficient vehicle. Each are doing the right thing.

  54. Justafan says:

    Another point I think I clearly made is that I can’t type for squat.

  55. katewrath says:

    I see the larger point here — if you drive a gas guzzler and don’t want to switch to a Toyota Echo, don’t despair.

    But the nutty thing about this equation is that no one is going to go out and get a car with terrible gas consumption just so they can really stick it to those Prius owners next door.

    If you’ve had good gas mileage for years with your (ahem) Honda Civic, you’ve already banked THOUSANDS of dollars that haven’t gone into your Land Barge ™. So if you do switch to a Prius, maybe you don’t see the kind of OMG, let’s buy a pony! jackpot that the downsizing Land Barge owners would see.

    On the other hand, all that spent gas money isn’t on your credit card racking up interest charges, or drained out of your home equity line, or keeping you from affording health insurance or…

  56. Carencey says:

    @dondiego87: nice examples. the family is saving the most money, but the couple is still spending the least. I’ve seen this same line of math used to explain why it actually makes more sense to use hybrid technology to improve mileage of big cars than to improve mileage of little cars which already get better mileage to start with.

  57. Lets stop throwing in the confusing math equations here. 25 mpg = 25 bloody mpg. Which is really not that good, considering that there are cars from the 70’s which got over 40 mpg. (Honda Civic being the one I’ve heard most about)

  58. Jamezspot says:

    I think the braniacs over at CNN decided to pick up Dan Ariely’s book and then decided to APPLY the knowledge from said book to maybe help some people out!

  59. christoj879 says:

    @sleze69: Yep. I went from a ~14 MPG gas truck to a ~24 MPG diesel Benz, and my cost went from ~$0.25/mi to ~$0.20/mi.

    Add biodiesel into that equation and the numbers get prettier.

  60. D.B. Cooper-Nichol says:

    The problem with the article isn’t the thesis, but the execution – it treats the family who “saves more” as the winner, as opposed to the family who “spends less.”

    First, I never knew it was a contest. Second, it’s like pointing out that a fat guy who went from 300 lbs to 250 “lost more weight” than the guy who went from 185 to 165, and calling the second guy’s weight loss “an illusion.” Yeah, it’s literally true, but it’s ultimately confusing (if not misleading).

  61. The Porkchop Express says:

    @PunditGuy: after two kids, it gets harder to fit in a regular car. By after two kids I mean…three or four, especially four. and depending on age you have car seats that take up more space than asses would.

  62. GreatCaesarsGhost says:

    @D.B. Cooper-Nichol:
    There isn’t a winner. The point is the family would be less inclined to make the change then the couple, even though they would benefit more.

  63. MajorXP says:


    In the end I could care less about MPG. I care about $ per mile.

    MPG Cost/Gallon
    1 $4.00
    5 $0.80
    10 $0.40
    15 $0.27
    20 $0.20
    25 $0.16
    30 $0.13
    35 $0.11
    40 $0.10
    45 $0.09
    50 $0.08
    55 $0.07
    60 $0.07
    65 $0.06
    70 $0.06
    75 $0.05
    80 $0.05
    85 $0.05
    90 $0.04
    95 $0.04
    100 $0.04
    105 $0.04

    Easy to see here how there are diminishing returns.

  64. Rusted says:

    @battra92: A minivan might be more suitable, or if there is a problem with roof height, a full sized van with even more room then a truck chassis type station wagon.

  65. Ailu says:

    Dang, this article has some funky math.. wonder where this news release originated.. GM perhaps?

  66. teexcue says:

    If you’re smart and look at things from an environmental and overall cost perspective, 200 gallons<500 gallons. Cheaper, and better for the world.

  67. @D.B. Cooper-Nichol: The family who does the most to save the environment the winner. For me, that means I’m willing to pay extra to use less energy.

    I understand that some people need to be hit where it hurts (the pocketbook) to get them to change. But It’s not like saving the world is free. It makes perfect sense for something with greater efficiency to cost more up front and quite possibly not even save money in the long run.

  68. @Corydon: I’m going to be the annoying guy who points out that my bicycle gets 0 gallons per mile or ∞ miles per gallon :P

    Nah, you can calculate the number of calories you burn while riding and convert that to an equivalent amount of gasoline. A quick calculation says I get about 3500 miles per gallon when riding at 13 mph. Still pretty good.

  69. whinypurist says:

    @Michael Belisle and Corydon: But what kind of food do you eat to get ~30,000 calories for only $4.00? Given the cost of human fuel, it’s hard to justify a switch from car to bicycle on purely financial terms.

    Re: the post, can I hope this kind of logic creates a market to sell the horrible, horrible Chevy Impala my husband opted for a couple of years ago to a truck/SUV driver who’s not ready to do the Prius/Civic/Echo thing quite yet? Nah, probably not.

  70. reykjavik says:

    Really?? You mean SPENDING more money doesn’t save you money??? Hmm… thats a basic concept only Americans can’t seem to figure out.

    Only Americans would think its good math to walk around with credit cards, statistically spending 20% more than those without credit cards, because they get 1% back from Visa!! (for you retards out there, thats a LOSS of 19%)

  71. @whinypurist: Mostly irrelevant. That only matters if you’re minimizing your exertion to save money. If you’re exercising anyway, the point is moot from a purely financial standpoint. Even so, we can learn some things by exploring the line of thinking.

    Biking uses 35 calories / mile. My car uses 1,250,000 cal / mile. Emissions for the bike? Nearly zero. The winner for the environment is clear.

    The financial savings are not great: A $4 box of granola bars is good for 30 miles of biking. So, right now, it’s about the same as my Honda Accord on a highway.

    And the cost brings us back to my first post here: I’m willing to pay more to save energy. Here, I pay about the same amount per mile, but the car uses around 35,000 times more energy. That should be an easy choice.

  72. battra92 says:

    @Rusted: It depends. My dad bought it back in 2001 and junked it last year. Gas was relatively cheap back then so he didn’t complain too much about it.

    When he junked it he got 15mpg and now gets 20 on his Tacoma. I showed him MajorXP’s chart and he somewhat gets the point but still grumbles.

    He hates station wagons so that was never an option. ;) Vans are also a PIA and still guzzle gas.

  73. whinypurist says:

    @Michael Belisle: After thinking about the math (using 1000 mpg for person bicycling) it actually could make sense financially for someone using a car with lower MPG or subsisting on relatively inexpensive, high-calorie food (i.e. your granola bars) to switch over to logging bike miles.

    But, in fact, I am one of those folks for whom the trade-off with human fuel is relevant, which is why I brought it up. This spring I contemplated switching over to biking to do my limited weekly driving (so my V6-owning husband could use our civic for his commute). But with a toddler always in tow, and trouble meeting my daily calorie needs already (plus the cost of the gear) – I decided it was a bad idea. I just can’t add enough food into my day to compare with what I get from my car.

    More recently I’ve been contemplating just switching cars with him – so don’t judge me for my V6 – I’ll be making a huge sacrifice!

  74. katylostherart says:

    i love this “large families” thing. most american families have one or two children. if you can’t fit 3-4 people in a midsized sedan, you just fail at life or need to diet. i drive a honda civic and many many times it has fit 3-4 adults and a baby seat, plus stroller and baby supplies in the trunk and a full week’s worth of groceries.

    what a bullshit excuse. just because you WANT the half ton towing capacity 4wd v8 suburban with the DVD player to take your ONE child to elementary school (1 mile down the road) doesn’t mean it’s actually difficult to downsize to, say, a honda accord.

  75. bonzombiekitty says:

    @Coder4Life: It’s not crap, they are making a comparison against the two families, not against what each family previously spent. The point is more of, if you have two cars like a decently efficient sedan that gets 30MPG and a not as efficient station wagon that gets 20MPG and are going to replace one with a new car, which one would you replace all other things being equal – the 30 MPG sedan for a 40MPG sedan or the 20 MPG station wagon for a 25 MPG station wagon? A lot of people would say replace the sedan since it has the greatest increase in MPG. But in reality, upgrading the station wagon is a better choice.

    @katylostherart: I find it funny too. We did grow up with a mini van as a second car, but we still had plenty of times when we’d all get crammed into the mercury tracer without much of a problem. The van was really only fully useful for moving stuff occasionally and vacations. Other than that, we’d fit into the smaller cars just fine.

  76. Bruce Bayliss says:

    The name of the game is to use as little fuel as possible. Comparing “before and after” mpg as a percentage is a fairly futile exercise.
    Just calculate the cost of transporting the tribe from A to B, factor in the increased cost of the more fuel-efficient car and the assumed future cost of fuel, look at its depreciation rate, amortise it over x years.
    Easy as that.
    Oh yeah, and reduce your fuel consumption by driving sensibly.
    I’m up to 40mpg (from 26mpg) by setting the cruise control to 65mph instead of 75mph, this on a Saab 9.3 Turbo on European motorways.
    And if I was to really let rip I’d be somewhere under 20mpg…

  77. jdjonsson says:

    I’ve started driving slower, and a tank of gas is lasting me longer. Yes, I’ve become the putt-putt driver going 65-70 on the freeway. At least I keep to the right lane most of the time.

  78. shifuimam says:

    This is an awesome post, because I just bought a new car with fuel economy (among other things) in mind. I had a 2000 Grand Prix GT that got about 16mpg in-town. However, what I wanted more than fuel economy was capacity to carry stuff after going to the hardware store, IKEA, etc. I looked at the Honda Fit, which has decent cargo room and gets about 30mpg.

    However, given that I rarely drive anymore (I take the bus to work now), I did the math and figured out that it would literally take years to recoup the $6500 price difference between the Fit and the car I ended up buying (a 2005 Hyundai Tucson GL). It was worth it to me to save the money, get slightly worse fuel economy, and still get what I wanted out of my car – a warranty and cargo capacity.

  79. BlazerUnit says:

    @Chris Walters: You nailed it.

    You either have two choices for saving money on fuel:
    1) Drive less altogether
    2) DON’T drive less, but drive the same distance using LESS fuel

    Number two is easier said than done if you actually use haul family and stuff in a large car or SUV, or you use your own wheels as a delivery vehicle. A modest improvement in MPG (combined with driving conservatively, like you should be doing anyway) means that you don’t have to sacrifice much space or utility.

  80. BlazerUnit says:

    @jstonemo: Understanding the your point about REAL costs of a newer fuel-efficient vehicle–it’s moot because we’re talking about the GALLONS PER MILE figure and not any other hidden costs.

    The hidden $3000 you have in savings to afford a scooter or low-end motorcycle is just as meaningless as your new $400 per month car payment. MPG figures don’t take financing into consideration, so you shouldn’t insist upon it when talking about GPM.