Gallons of Fuel vs. Miles per Gallon

Discussion in 'Environmental Discussion' started by cycledrum, Mar 18, 2011.

  1. cycledrum

    cycledrum PSOCSOASP

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    Due to the effect of diminishing returns of very high fuel economy ratings, more gasoline might be saved* by improving gas guzzling vehicles or getting drivers to downsize than by pushing the boundaries of exotic vehicles like 60 MPG+ concept cars.

    * Assuming owners would drive the same miles per year in the more efficient vehicle as the less efficient one.

    Per 400 mile* trip, the same amount of fuel can be saved in switching from (or converting) a 20 to a 30 MPG vehicle (6.7 gal) as you would in switching from a 30 to a 60 MPG vehicle (also 6.6 gal).

    *Note - 400 miles is a fairly normal tank range for many passenger cars and trucks.

    My point is not to belittle the quest for exotic MPG cars like 60 MPG or more, but to drive home the point that Gallons vs. MPG is a non-linear function. The lower you go in miles per gallon, the steeper the gallons used curve. The higher the MPGs, the flatter the gallons curve, resulting in less difference of fuel used.

    So, as much as I respect the push for cars above 50 MPG* it seems that improvement from 15 to 25 MPG (Tahoe to Highlander Hy) for example could have a larger impact on fuel savings (10.6 gallons saved).

    * getting 100MPG on your PHV would save 4 gal in 400 mi over reg Prius, not including electric usage

    - Not that we shouldn't be improving everything in the spectrum.

    - Emissions reduction not considered

    MPG : Gallons / 400 mi
    10 : 40
    15 : 26.6
    20 : 20
    25 : 16
    30 : 13.3
    35 : 11.4
    40 : 10
    45 : 8.9
    50 : 8
    55 : 7.3
    60 : 6.7

    View attachment galvsmpg.xls
     
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  2. CheeseheadPrius

    CheeseheadPrius Junior Member

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    Well, I went from an 18 : 22 to the Prius 50 : 8. That's if I can hold a 50mpg avg. Interesting chart though. Something I never looked at laid out like this.
     
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  3. darelldd

    darelldd Prius is our Gas Guzzler

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    Yes indeed. Way better to get the 10 mpg vehicles up to 20 mpg than to get a 50 mpg vehicle up to 100 mpg.

    And all this would be way more obvious if we weren't stuck on this silly mpg business, and instead worked with gallons per X distance - like they typically do in Europe.

    MPG assumes that we care about how many miles we drive, more than the amount of fuel. GPM is the better measure, and concentrates on the amount of fuel used.
     
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  4. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    As much as I hate to defend GM at any time, their 2 mode hybrid trucks are way more effective than they are given credit for. They are addressing the vehicles that need the most help.

    (I read about folks travelling a longer distance to 'improve' their MPG and I think "Madness". If they focused on fuel used they would never make that mistake)
     
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  5. john1701a

    john1701a Prius Guru

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    It certainly gives that impression, but in reality sales are almost nonexistant. 28,172 Silverado pickups were purchased last month. Only 47 of them were Two-Mode. Over the past 3 full years, spread across 5 different models, less than 22,000 total have been purchased.

    The concern about "too little, too slowly" is certainly valid. While the technology may look worthwhile, it really hasn't accomplished much.

    Sadly, the same situation appears to be playing out with Volt now.
    .
     
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  6. Corwyn

    Corwyn Energy Curmudgeon

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    This is true due to the inverse relationship (per gallon). However, I am not in a position to take advantage of it. I just traded my 30 MPG Subaru in for a 50 MPG Prius. Now I am trying to get 60 MPG from it. Individual actions are necessary to affect the change, I wish to see; and 100 Million people each decreasing their gas consumption will accomplish more than Toyota improving their worst performing vehicles. We do need both, of course.

    No one is done. We are still headed in the wrong direction, speeding, and accelerating.
     
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  7. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    I blame the 'if it is a hybrid, it should get 50 MPG' for that. GM certainly has not advertized Gallons saved per 1000 miles, by EPA rules, perhaps they can't.

    Silverado Hybrid 44 20 MPG @ 1000 miiles = 50 gallons @ $3.50 = $175

    Ford F-150 4X4 14 MPG @ 1000 miles = 71.4 gallons @ $3.50 = $250

    Once purchased, it will save 21.4 gallons every 1000 miles, but it will take 160,000 miles to pay the difference in list price. (assuming no more increase in gas price. Yeah, right)

    Chevrolet | Competitive Comparison
     
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  8. avocadoman1

    avocadoman1 Member

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    in an effort to manage my budget and total dollars spent, i generally analyze my driving in "cost per mile".

    that is, when gas is $4/gallon...
    - my 15mpg truck costs $.27/mile
    - my 20mpg SUV costs $.20/mile
    - my 50mpg Prius costs $.08/mile
     
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  9. cycledrum

    cycledrum PSOCSOASP

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    Yes! Bravo! Very well said!

    I was thinking the very same thing this morning. If we must stick with the $%^&$ English (sp?) measurement system, how about -

    Gallons per 100 miles (Prius : 2 /2.1 GP100M)

    Chevy Tahoe : 7.1 / 5.3 GP100M

    ... L / 100km would be better.
     
  10. qbee42

    qbee42 My other car is a boat

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    It would help if people could do basic math. It's shocking how little "gut feeling" most people have for even simple mathematical concepts. Our educational system has failed them.

    Tom
     
  11. cycledrum

    cycledrum PSOCSOASP

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    That and our movie / TV / pop culture's habit of worshiping professional athletes and entertainers while mocking engineers and scientists as nerds with thick glasses and pocket protectors .... but I digress.
     
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  12. mikewithaprius

    mikewithaprius New Member

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    If somehow someone/we/whoever could appeal to the financial side of things, it seems that would help bring attention to the amount of fuel used instead of miles over a gallon (I had read somewhere recently that people buying hybrids tend to drive more because they think that's OK with better mileage).

    I like how fuelly, for example, shows potential savings for the latest fillup, highlighting your point of limited fuel savings in higher mileage cars from a dollars and cents point of view.

    From a random Suburban getting 11.9 mpg last fill-up, it shows they could have saved $14.08 getting 3 mpg better, while I would only save $1.24 getting 3 mpg better.
     
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  13. ksstathead

    ksstathead Active Member

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    Manufacturers ought to give US drivers a choice (at least) of L/100km or G/100mi. Given the fact that L/100km is a (non-US) world standard and the fact that we are driving computers, this seems a reasonable and almost trivial enhancement.

    Further, we should have fuel cost as an input to the car, and it could show cost per mile with trip A/B info.

    And while at it, they should go ahead and let us choose which scangauge gauges we want to display on the car screens.
     
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  14. DaveinOlyWA

    DaveinOlyWA 3rd Time was Solariffic!!

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    ok, so if 100 mpg vehicles are not possible and our only option is to get rid of 10 mph vehicles, i could agree with this, but i cannot.

    my goal is not a 50% reduction in foreign oil imports. its 100% reduction and we cant do that by blowing thru 20+ gallons on every tank
     
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  15. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    I suspect the truth is that folks who already drive many miles each year have purchased hybrids more than the general populace. If your mileage is not flexable, then the only way to save money is with MPG. I only get paid for going to the client's site, so I am going, but in a Prius.
     
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  16. cycledrum

    cycledrum PSOCSOASP

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    1. Ford F-Series
    2. Toyota Camry
    3. Chevrolet Silverado
    4. Honda Accord
    5. Toyota Corolla
    6. Honda Civic
    7. Nissan Altima
    8. Dodge Ram
    9. Ford Fusion
    10. Honda CR-V

    Top 10 best

    Above list of top 10 selling cars and trucks in US for 2009 (sorry rest of world!). Excluding hybrids, the 5 highlighted are basically 25 MPG average cars.

    If in some years, those 5 become a Prius v type vehicle at 40 MPG, would reduce fillup from 16 gallons per 400 miles down to 10 gallons gas for the family hauler.

    I think width in those top 5 models is critical - they really want to fit 3 across in the back. Camry is 72", Prius v is 70". Maybe increasing v by 2" width later on could capture those slots. I don't think people are going to get any slimmer!

    The Civic / Corolla / Cruze owners can migrate to Prius, Leaf or better.

    Can heavy duty pickups get boosted to 25 MPG? Hope so.

    I'm just thinking what can be done to save resources and still meet needs in xx years.
     
  17. darelldd

    darelldd Prius is our Gas Guzzler

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    Yes, if we aren't bright enough to actually start using our official national system of measurements (metric!) then Gallons per 100 miles is a good choice. Using this measure, we can actually compare vehicle efficiency more easily, and come up with valid CAFE average numbers - instead of the way the CAFE numbers are gamed now when using mpg. The whole "averaging mpg numbers" thing really bugs me. I think if this topic is brought up enough times, eventually (I hope!) something will change. When I started driving, I never thought about why other countries used fuel volume per distance. Seemed so complicated just because it was different from what I was used to. And I didn't really care all that much. I just knew that I higher number was better. More miles! Yay! It wasn't until somebody long ago made a comment similar to the OP's here that I finally sat down and scratched my head... and realized how silly we are to be using distance per volume of fuel. the logic just escapes me. How did we get here? Ignorance or by design? Neither one makes me very happy! I hope this thread will bring a few more folks into the fold - in realizing how we should be doing this.

    So true. Sadly.
     
  18. Mendel Leisk

    Mendel Leisk Senior Member

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    I'm often taken aback by the shear mileage a lot of PriusChat members rack up. If you've got a vehicle, all well and good to use it, but if your trips are a combination of:

    1. Short local runs for groceries, errands, etc.

    2. Moderate or long daily commutes to workplace.

    3. Occasional weekend forays to recreation destinations.

    4. Long haul vacations, maybe yearly.

    Consider leaving the car parked for #2, and take public transit instead.
     
  19. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    When I lived in Aberdeen WA, Seattle WA, and Toronto ONT, I used public transportation a great deal. Both Elko NV and here in Greenwood MS, no such choice is available. (in Elko, I took private buses 100 miles a day) Even if public transportation was available, since I travel to a different client in a different town each day, I would be challenged to use it.
     
  20. hyo silver

    hyo silver Awaaaaay

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    Litres per 100km makes sense to me. Still, that mpg thing is pretty pervasive. Metric is *so* much easier and far more logical - all that dry or liquid, troy or avoirdupois crap is ridiculous nonsense. Too bad it's so difficult to 'unlearn' things.