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Old 06-29-2008, 09:52 AM   #1 (permalink)
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Math behind MPG

Please correct me if I am wrong.

a) 12MPG at $5 per gallon over five years with 15000 miles per year
is a result of $31250

b) 24 MPG, everything else the same, is $15625
c) 48 MPG, everything else the same, is $7812

going from 12MPG to 24MPG gets $15625 back to you over five years

going from 24MPG to 48MPG gets $7812 back to you over five years

going from 48MPG to 96MPG gets $3906 back to you over five years

Yes I realize that if gasolene gets to $10 per gallon, savings will double.

*************

point is, hypermiling mpg savings is mathematically not paying back at a certain point (personally decided). In five years it is a good time to switch to PHEV, to save more than ecomodding, as maybe some international company will have it right.

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Old 06-29-2008, 11:08 AM   #2 (permalink)
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Evil Pumpkin - '08 Scion xD RS 1.0 #1633
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I think your only flaw is, as the cars become more economical mpg wise, we will still be able to hypermile them extending their posted ranges.

Therefore the saving will still remain constant over time. Just because a window sticker says it does 45mpg definately doesn't mean everyone drives it to get to that range.

We on the other hand strive to double it, thereby saving more money than what a straight formula can predict .. IMO
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Old 06-29-2008, 11:12 AM   #3 (permalink)
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I believe you have it right. The thing about MPG is that it doesn't actually tell you how much fuel you are using. Gallons per 100 miles is much more useful.
For example:

12.5mpg = 8gal/100mi
25mpg = 4gal/100mi
50mpg = 2gal/100mi

et cetera.

As such, improving the least-efficient vehicles cuts fuel use fastest. Squeezing 15mpg out of a truck that gets 12 or 13mpg normally saves more fuel than getting 35mpg out of a car that usually gets 32 or 33mpg.

It's not that hypermiling mpg doesn't pay, it's just that the returns in terms of dollars and gallons of fuel saved diminish. It's always effective to improve efficiency-- it's just not a linear relationship between the effort expended and the gains achieved.
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Old 06-29-2008, 11:29 AM   #4 (permalink)
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That is why I like the truck fairing modification in the other forum. Getting improvements in typically low MPG vehicles (like pickup trucks) gets more overall savings for everyone.

Also, I appreciate the comments about better distance per tank of fuel. That saves on stops, which can exponentially eat up MPG.
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Old 06-29-2008, 11:36 AM   #5 (permalink)
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Looks right over 5 years.

Does anybody have a place to host files? I have an excel file that I made up to be somewhat user friendly. You can enter in years, mileage or kilometers for each vehicle you own (up to 4), etc..

Looks like as good a thread as any for it.
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Old 06-29-2008, 11:45 AM   #6 (permalink)
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NewBlue - '07 Honda Civic EX
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I figure if I save $100 in 5 years or $3500 in 5 years it's money in my pocket and not in the oil company account.
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Old 06-29-2008, 12:19 PM   #7 (permalink)
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I didn't read much about this hosting place, but let me know if the link actually works for people.

Gas Mileage Calculator Rev 0.xls

Theres a tab for metric and a tab for Imperial - US
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Old 06-29-2008, 02:44 PM   #8 (permalink)
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I think you're wrong in the way you look at the numbers, going from 12 to 24, 24 to 48, etc. Why the intermediate jumps? If 96 mpg is an available option, then the only step should be from 12 to 96.

Also, you have to realize that for some of us, it's about using less gas. If it saves money too, that's great, but I'm willing to spend somewhat more to burn less.
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Old 06-29-2008, 06:53 PM   #9 (permalink)
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12 to 24 MPG is truck to car - costs $10,000 to buy used over five years with all expenses (worst case)

24 to 48 MPG is car to HYBRED - costs $30,000 to buy new over five years with all expenses (worst case)

48 to 96 MPG is a hypermiler vehicle - unknown cost
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Old 06-29-2008, 07:28 PM   #10 (permalink)
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Quote:
Originally Posted by Blue07CivicEX View Post
I figure if I save $100 in 5 years or $3500 in 5 years it's money in my pocket and not in the oil company account.
Switching to '05 Civic (45+mpg) from '06 RAM (15.8mpg) as daily driver is money in the bank even after purchasing the Civic. Why? I'm using 33% of the fuel, regardless of fuel costs.

Therein, I'm spending that on developing equity in my vehicle which will still be worth something after the recovery period (4 years @ 3.75/gal) is over. Otherwise, I'd be blowing >$10K out the exhaust pipe which does nothing for me, you or the environment. After 4 years, I'll still have Servicable Ecomodded ride worth something! As gas prices go up, my recovery period shortens, and the value of my Civic is higher!

Win - Win - Win

The 2006 RAM has been resigned to Tow Duty only, and will recieve suitable Aero mods over the next several months. The 2005 Civic will recieve additional mods, getting average mpg higher, further reducing recovery period.

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