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Old 03-06-2011, 02:03 PM   #11
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Re: Efficiency is NOT MPG

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Originally Posted by theholycow View Post
Your truck must not be a half-ton. I assumed so because it has a V6 but I suppose that they put the V6 in the heavier models back then.etc etc etc etc
Holy Hijack Batman!
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Old 03-06-2011, 03:24 PM   #12
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Re: Efficiency is NOT MPG

The way to measure your fuel economy is MPG. End of story.
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Old 03-06-2011, 06:36 PM   #13
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Re: Efficiency is NOT MPG

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The way to measure your fuel economy is MPG. End of story.
I think that what the OP is saying is that, especially for this shipping and freight industry, MPG is not enough. A large truck doubling its MPGs at the expense of half its carrying capacity is really a wash. How about "Ton-Miles/gallon," or "how many tons can I move one mile with one gallon of fuel?"


Here's a practical example: Say you're moving, and you need to rent a truck. There are two sizes available. The super-hauler holds 300 cubic feet of stuff and gets 15 mpg. The smaller truck holds 200 cubic feet of stuff and gets 20 mpg. You have 250 cubic feet of stuff. Which do you pick?
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Old 03-06-2011, 06:46 PM   #14
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Re: Efficiency is NOT MPG

OP has a very good point but trying to include weight as well as fuel used for econo calculations would quickly get onerous. Most people are barely capable of calculating mpgs, much less knowing how much thier rig weighs. And the potential for errors in the calculated results gets pretty bad too without good weight info... perhaps there needs to be a scale next to every pump?
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Old 03-06-2011, 06:51 PM   #15
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Re: Efficiency is NOT MPG

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The way to measure your fuel economy is MPG. End of story.
The way to measure the Car's efficiency is MPG. However, I believe Howard is more efficient to not waste our motions. For example, I have 2 vehicles, one of which averages around 31 mpg and one that averages around 40. If my wife and I were to both drive somewhere together, does it not make sense for us to ride together when possible (if you can deal with the nagging...)? If my brother and his wife were making a 100-mile trip and rode together in their 22 mpg SUV, I believe they are being more efficient than my wife and I would be if we drove our 2 cars separately. Our vehicles would have to average 44 mpg to break even with them.
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Old 03-07-2011, 12:54 PM   #16
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Re: Efficiency is NOT MPG

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Originally Posted by theclencher View Post
OP has a very good point but trying to include weight as well as fuel used for econo calculations would quickly get onerous. Most people are barely capable of calculating mpgs, much less knowing how much thier rig weighs. And the potential for errors in the calculated results gets pretty bad too without good weight info... perhaps there needs to be a scale next to every pump?
Weight of the vehicle itself has no place in the calculation, weight of the payload does. A single person in an automobile is probably around 180 lbs average... maybe more for modern Americans. When I mentioned the semi, I mentioned ONLY the payload of 60,000 lbs or so, not the total weight of around 80,000. What matters is how much WORK we get out of a gallon of gas.
You can spend a lot of time and money trying to get your car from 40 up to 50 mpg, but if you simply drive with two passengers instead of one, the efficiency, you are in effect doubling your mileage in terms of work done.
If we can capture waste heat, and use it to replace other fuels that we heat our homes with, we can perhaps double or more our efficiency

Increasing gas mileage is an endeavor of diminishing returns..... We can gain quite a bit initially just by changing our driving habits, and inflating our tires, and various other tricks, but after the initial gains, each one becomes more difficult to achieve. More time and money for less gain. This is the case with many other areas. Diminishing returns.

The most dramatic results we can achieve are by carpooling and taking public transportation, bicycle, walking, etc. Those gains are many times what we can achieve in simple "gas mileage" improvements. The object here really is to SAVE ENERGY... and on a more personal level $$$$

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Old 03-07-2011, 01:04 PM   #17
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Re: Efficiency is NOT MPG

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The object here really is to SAVE ENERGY... and on a more personal level $$$$
Well, that's where things get complicated. Different folks on this site have different goals for what they learn here. Sometimes that muddles discussions. My goals are saving money, having a hobby, learning more about cars, and maybe conserving oil/lowering dependence on undesirable oil sources. Other people are here to have fun doing something competitive (getting the most MPG at all costs) or maybe to save the environment (perhaps with lower emissions, lifecycle analysis of the vehicle as a whole, or reduced dependence on oil whose mining may hurt the environment)...and probably some motivations I forgot.
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Old 03-07-2011, 07:21 PM   #18
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Re: Efficiency is NOT MPG

I cringe at the thought that my old vanpool's Dodge Maxivan, even if it only got 10 mpg, was one of the most efficient vehicles on the highway, short of commuter buses. It was always filled with 13-15 people, so it was getting ~140 peoplempg @10 mpg, and ~210 pmpg @15 mpg. That's as good as a Prius loaded to capacity.
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Old 03-07-2011, 10:48 PM   #19
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Re: Efficiency is NOT MPG

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Weight of the vehicle itself has no place in the calculation, weight of the payload does.
I disagree; the drivetrain doesn't just propel the baggage down the road; it has to expend energy on the entire vehicle and contents.
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Old 03-08-2011, 06:21 AM   #20
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Re: Efficiency is NOT MPG

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I disagree; the drivetrain doesn't just propel the baggage down the road; it has to expend energy on the entire vehicle and contents.
You're both right, just talking about two different things. From an absolute perspective, yes, you absolutely must include the weight of the vehicle to calculate the work being done.

I believe what Howard means is that the weight of the vehicle isn't doing anything useful.

Consider: using a 60,000lb truck to move a 1lb box vs a 2,000lb car to move a 1lb box. From a pure physical standpoint, the truck is doing more "work." But which one is more likely to have a better mpg-to-cargo ratio?
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