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Old 05-21-2012, 05:14 PM   #1 (permalink)
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10 to 12 mpg improvement is the same as 30 to 60 mpg

So I got my spreadsheet out and low and behold it works out that Vehicle A going from 10 mpg to 12 mpg at X miles/year will give the same reduction in number of gallons/year as Vehicle B going from 30 mpg to 60 mpg, when both vehicles travel the same number of miles. This seemingly paradoxical calculation is probably well known on this forum but I think Joe Public and Joe Politician or even Consumer Reports do not seem to know this. When you hear Consumer Reports saying A/C use give about a 1 mpg reduction.

Or when going from 10 mpg to 12 mpg is reported as 20% improvement is reported as being equivalent to another vehicle going from 30 mpg to 36 mpg as also a 20% improvement and mistakenly concluding that, as both were 20% improvements in mpg, that they have equal fuel consumption reduction impact. That's right motoring press even % improvements in mpg are not comparable.

I wonder if the 2 or 3 mpg differences once you get into the high 40s, low 50s are sometimes given too much emphasis.


Last edited by briank; 05-21-2012 at 05:36 PM..
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Old 05-21-2012, 05:22 PM   #2 (permalink)
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..."ratios" will do that to/for you.

...ain't playing with numbers a lot of FUN?

1.2 = 12/10

...but:

2.0 = 60/30

Last edited by gone-ot; 05-21-2012 at 06:35 PM.. Reason: added examples to support tjts1 answer below
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Old 05-21-2012, 06:23 PM   #3 (permalink)
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Quote:
Originally Posted by briank View Post
10 to 12 mpg improvement is the same as 30 to 60 mpg
no
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Old 05-21-2012, 06:39 PM   #4 (permalink)
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Quote:
Originally Posted by tjts1 View Post
no
1.67 gal saved per 100 miles, either way.
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Old 05-21-2012, 06:41 PM   #5 (permalink)
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Quote:
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I wonder if the 2 or 3 mpg differences once you get into the high 40s, low 50s are sometimes given too much emphasis.
At this level, it's a competitive sport, done for fun. Nothing wrong with a little fun.
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Old 05-21-2012, 08:41 PM   #6 (permalink)
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Quote:
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1.67 gal saved per 100 miles, either way.

Agreed, the only difference is (for an average vehicle) it's much easier to go from 10mpg to 12mpg than 30 to 60 mpg.
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Old 05-21-2012, 09:16 PM   #7 (permalink)
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Quote:
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1.67 gal saved per 100 miles, either way.
No and you're missing the point.
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Old 05-21-2012, 09:18 PM   #8 (permalink)
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Yes, the MPG Illusion.

Duke Professors Jack Soll and Richard Larrick discovered this a while back - that mpg works in terms of diminishing returns such that gains made on fuel thirstier vehicles save more fuel.

In truth, and they articulated this in the video, mpg is a poor measurement of FE, for the simple fact that it isn't linear.
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Old 05-21-2012, 09:55 PM   #9 (permalink)
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Exponential function anyone? I understand that the majority of people on this board who are above 35mpg are doing it for fun, but above that rate there's not a lot of money to be saved for the amount of effort involved. I was getting about 25mpg average last summer, id be ecstatic to hit 30mpg combined this summer, but above that i wouldn't save much money.

at my 300miles a week, id save about $30 a month going up to 30mpg. but going from 30 to 35mpg id only save an extra $20. if you made an astronomical leap from 50mpg to 80mpg average, you'd save just barely over $30 a month.
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Old 05-21-2012, 10:08 PM   #10 (permalink)
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Quote:
Originally Posted by tjts1 View Post
No and you're missing the point.
No AND I'm missing the point?

Let's start with the "no". There's NOT 1.67 gallon saved per 100 miles, either way? How much IS saved in each 100 miles driven, in each situation?

I agree that I don't see your point, though. Help me.

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