A new metric for fuel economy

DeadPhish · May 8, 2006

Allow me to add this for your consideration. I am beginnng now, here, to promote in every venue and every conversation ( I sell Toyota's, emphasizing the hybrids, and own a Prius II ) that the method for comparing vehicles' fuel economy ratings should be changed to 'GPC' (Gallons per 100 mi).

GPC is not my idea although I have used a similar idea in past comparing different vehicle's fuel economy. GPC to my knowledge is first proposed as a metric for fuel economy in the most recent R&T article article comparing hybrids. It's elegant and simple. As R&T notes GPC or it's metric version is the normal way economy is measured in the rest of the world as 'liters/100 km'. Until the American public brings itself into the 20th century by adopting the metric system in daily use ( it has been, btw, the official system of measurement for the Federal Gov't since the mid 80's ) we are stuck with outdated, Middle-Ages terminology.

GPC is simply calculated by (dividing Gallons used by miles driven ) then multiplying by 100. It's the same process everyone now uses, except changing the variables ( dividing miles driven by gallons used ). So why propose a change?

Responsibility.

The difference in the two following statements is Responsibility.
'I get 47.2 mpg on average.'
'I use 2.1 gallons every 100 miles I drive'

One is almost a contest encouraging consumption. 'I can go farther than ...' The latter makes me consider what I use to get where I'm going. In addition now there is another readily available statistic which is very important at this time and likely into the future.

How much does it cost me to go 100 miles?

At 47.2 mpg it's not obvious what the cost of this drive actually is. But in using 2.1 GPC it's an easy exercise to see that it costs me about $6.30 at today's prices.

Which brings me to why is the US system of measuring fuel economy still in use whereas the rest of the world uses 'l/100 km'. We in the US have not been perceived as being as personally responsible as the rest of the world in our use of resources. MPG plays into this by making FE a theoretical game rather than a personal commitment. Marketing plays into this as well as certain numbers like '50' and '60' get promoted. One might even envision the fuel providers and the vehicle providers being on the side of maintaining the status quo, albeit for differing reasons.

Challenge: Think about fuel economy in terms of your personal responsibility in using as little as possible.

Herebelow are some easy examples:
Our ICE V6 Highlander uses 5 Gal/100 mi, 5 GPC on average. which currently is $15/100 mi ( or $2250 / 15000 mi )
My previous 4c Camry's used about 3.3 GPC. which currently is $10/100 mi ( or $1500 /15000 mi )
My current Prius uses 2.1 GPC. which currently is $6.30/100 mi ( or $945 / 15000 mi )

I sell SUV's and trucks which use on average about 6 GPC. Current cost $18/100 mi

Note also the verb in each sentence describing fuel economy.

Bob Fogarty
DeadPhish

Change can begin with as small a step as refusing to give up a seat on a bus.

vtie · May 8, 2006

Good points, I think. Personally, I'm used to calculate fuel consumption as liter / 100 km. It always sounded more logical to divide the fuel consumption by the distance you travel, rather than divide the distance by the fuel consumption (the mpg approach).

Logically, what you start from is that you have to travel a certain distance (e.g. to go to work, to visit family), and then you want see how much fuel you need for that (which directly relates to the cost). You never do the reverse logic, something like "hey, I have 5 gallons, how far can I drive with that?"

Besides, when my Prius drives in electric mode, it displays "0 L/100km". I think that's nicer than "99 mpg", which is silly because what it really should say is "infinite mpg".

Another argument (maybe far-stretched, but elegant from a mathematical perspective) is that L/100km (or gallon/100 miles) is additive: if you travel the same distance with several cars (e.g. in a group), you simply add the numbers to come to the total consumption of the group.

Maybe this is just because I'm a mathematician...

darelldd · May 8, 2006

Very nicely explained... by both of you. I've only given this matter some passing thought, and now you have me convinced. That we don't use the metric system in the us is a travesty, and now I see better how our "mpg" measurement is just one more part of that inelegance.

For most people "change" is the enemy. Witness our non-acceptance of the metrric system, which by all accounts is superior to the random metrics we use in the US today. We don't change because it is different and maybe even hard to grasp the "new" terminology at first glance. That it'll be better for everybody in short order doesn't seem to matter. So the big question is: How can we possibly expect to change over to MPC when we can't even change to the metric system? I'm seeking the answer because when I become Supremem Ruler of ALL, I'll be making these changes. And I'd like to figure out how to do it in the most expedient way.

jbarnhart · May 8, 2006

I think your argument is persuasive enough without the "we're evil Americans and we don't do it like the rest of the world" stuff. I mean, c'mon, the numbers are reciprocals. It's not a huge deal, but it is slightly more convenient to figure out gas consumption from the GPC figure.

TonyPSchaefer · May 8, 2006

<div class='quotetop'>QUOTE(jbarnhart @ May 8 2006, 11:14 AM) [snapback]251483[/snapback]</div>

I think your argument is persuasive enough without the "we're evil Americans and we don't do it like the rest of the world" stuff. I mean, c'mon, the numbers are reciprocals. It's not a huge deal, but it is slightly more convenient to figure out gas consumption from the GPC figure.[/b]
Click to expand...

You're right in that the numbers and personal responsibility speak for themselves.
Perhaps that we are evil Americans could just be mentioned as a footnote.

kirbinster · May 8, 2006

Seems to me there are a hell of a lot more important things to do in this world than invert a fraction. What the heck difference does it make which term in a ratio is the numerator or the denominator? Mile per gallon is the same as gallons per mile - just the inverse ratio, but it tells you the exact same thing.

I could argue against your point just as easily as you argue for it. Why would I want something on the basis of 100 miles rather than one. I don't care how many gallons are used to go 100 miles. I want to know when I have one gallon left in my tank how far I can go, so miles per gallon makes more sense. The point is each is equally correct, but the standard is mpg just like the standard in this country is miles not kilometers.

A much better way to get people to think of fuel usage is to mandata that a Prius style MFD be installed in every new car so people will see instantaneously how they are wasting fuel - that would have much more impact on fuel usage than flipping a fraction upside down.

Tempus · May 8, 2006

I mentioned the R&T Metric in a rant a little while back, but I wanted to expand it.

I want to see ratings in BTU/100 Miles so we can easily compare efficiencies even when different fuel types are used.

darelldd · May 8, 2006

<div class='quotetop'>QUOTE(jbarnhart @ May 8 2006, 09:14 AM) [snapback]251483[/snapback]</div>

I think your argument is persuasive enough without the "we're evil Americans and we don't do it like the rest of the world" stuff. [/b]
Click to expand...

Wow. I didn't read "evil Americans" in the OP at all. Mildly retarded in respect to units, maybe - but not evil.

Seems to me there are a hell of a lot more important things to do in this world than invert a fraction.[/b]
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True! I'd first get rid of daylight saving time, switch over to the metric system (oh, wait, we've already donw that... I mean USE the metric system), change everybody to 24-hour time, promote whilred peas, and THEN I'd put our mileage calculation in line with the rest of the world. Wouldn't it be nice - in general - to have some world-wide standards so we would NOT have to waste so much time (and introduce so much error) on conversions? I worked in an industry that built microscope stages here in the states for a microscope mfg in Germany. Roughly 1/4 of our effort went into conversions of all our tooling and product to match the metric tooling and product of the mfg. Here in my shop I have two tools to do everything. SAE and Metric. Every try to find a metric hammer? Inverting the fraction is about the easiest thing we can do to achieve better standards.

A friend once said: Standards are great! The more the better.

TheForce · May 8, 2006

<div class='quotetop'>QUOTE(darelldd @ May 8 2006, 03:36 PM) [snapback]251635[/snapback]</div>

A friend once said: Standards are great! The more the better.
[/b]
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I always say that standards are GREAT because you have you have soooooo many to choose from.

We really do need to switch to the metric system. Only because I cant add, subtract, multiply and devide fractions. <_<

darelldd · May 8, 2006

<div class='quotetop'>QUOTE(Tempus @ May 8 2006, 12:35 PM) [snapback]251634[/snapback]</div>

I mentioned the R&T Metric in a rant a little while back, but I wanted to expand it.

I want to see ratings in BTU/100 Miles so we can easily compare efficiencies even when different fuel types are used.
[/b]
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That would likely need to come as well, yes. For now, we in the EV world use a silly "GGE" or Gallon of Gas Equivalent measurement... because it is about the only thing that people can quickly understand. Most people are surprised to find that my EV holds about 0.8GGE in its batteries, and can travel more than 100 miles. Or to look at it another way, my EV gets about 140 MPGGE. Would make WAY more sense to just use a unit of real energy for these kinds of comparisons.

nerfer · May 8, 2006

<div class='quotetop'>QUOTE(kirbinster @ May 8 2006, 02:21 PM) [snapback]251622[/snapback]</div>

Seems to me there are a hell of a lot more important things to do in this world than invert a fraction. What the heck difference does it make which term in a ratio is the numerator or the denominator? Mile per gallon is the same as gallons per mile - just the inverse ratio, but it tells you the exact same thing.

I could argue against your point just as easily as you argue for it. Why would I want something on the basis of 100 miles rather than one. I don't care how many gallons are used to go 100 miles. I want to know when I have one gallon left in my tank how far I can go, so miles per gallon makes more sense. The point is each is equally correct, but the standard is mpg just like the standard in this country is miles not kilometers.

A much better way to get people to think of fuel usage is to mandata that a Prius style MFD be installed in every new car so people will see instantaneously how they are wasting fuel - that would have much more impact on fuel usage than flipping a fraction upside down.
[/b]
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I (reluctantly) agree with this. The GPC does make a certain amount of sense, but fighting the inertia of change would take energy better used elsewhere. People already complain enough about the metric system, and many still aren't sure what to make of the hybrids. Having hybrid owners push another European convention on them would further alienate us. (I tell my dad, a minister, that if God wanted us to use the metric system he would've given us ten fingers and ten toes. He doesn't see the humor in that

We typically track our mileage for two related reasons: how far can we go on a tank of gas, and how far can we go before we need to fill up again. If we always thought about how much gas is used on a specific trip, then your method makes it slighty easier to compute. Vehicle specs often list the MPG and the cost per year of gas, based on given assumptions, or the gallons needed to drive X,000 miles.

But before changing that, I propose we get rid of this silly dual twelve-based mixed with a sixty-based time system. Of course, there's a compelling reason to ditch the whole ten-based metric system and go with the dozenal system (base 12) - it's divisible by more common elements, it's more efficient use of digits, we already sell numerous products by the dozen (including essentials like eggs, donuts, and beer), and then we can keep 12" to a foot, 12 hours in a half day, 12 disciples, 12 zodiac signs, 12 cards in a pinochle suit. And if you need to count on your fingers, just use all the finger knuckles on one hand, so then you can count higher before taking off your shoes!

nerfer

vtie · May 8, 2006

<div class='quotetop'>QUOTE(kirbinster @ May 8 2006, 09:21 PM) [snapback]251622[/snapback]</div>

Seems to me there are a hell of a lot more important things to do in this world than invert a fraction.
[/b]
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Wah! That's an argument you can use against 99% of the things people do. Seems to me there are a hell of a lot more important things to do in this world than post messages on PriusChat.

<div class='quotetop'>QUOTE(kirbinster @ May 8 2006, 09:21 PM) [snapback]251622[/snapback]</div>

What the heck difference does it make which term in a ratio is the numerator or the denominator? Mile per gallon is the same as gallons per mile - just the inverse ratio, but it tells you the exact same thing.
[/b]
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Just like in human language, a lot depends on how things are phrased. Believe me or not, but people do this constantly in physics and engineering, and they even invent new names for it.

<div class='quotetop'>QUOTE(kirbinster @ May 8 2006, 09:21 PM) [snapback]251622[/snapback]</div>

I want to know when I have one gallon left in my tank how far I can go, so miles per gallon makes more sense.
[/b]
Click to expand...

This brings me to the major problem I currently have with my prius: why doesn't it show this number? Any other car I have seen the last 5 years shows me the distance I can travel before emptying the tank. I don't need to know the gallons left in my talk (I don't even know how to figure that one out on the prius). I don't need to know the mpg at that moment, and I definetely don't want to do that calculation while I'm driving. I just want to see a number "distance to empty tank". BTW do you know how many gallons are left in your tank? Are you able to do this calculation with your prius? Have you ever figured out that you have "one gallon left in the tank" ?

darelldd · May 8, 2006

<div class='quotetop'>QUOTE(theforce @ May 8 2006, 12:46 PM) [snapback]251645[/snapback]</div>

I always say that standards are GREAT because you have you have soooooo many to choose from. [/b]
Click to expand...

Yup. That's the joke that I couldn't remember, and ended up butchering.

We really do need to switch to the metric system. Only because I cant add, subtract, multiply and devide fractions. <_<
[/b]
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Indeed. When I worked in construction, I don't know how many times we would screw up our fractions. Quick! What's 13' 4-7/8" minus 2-9/16" plus 132' 11-3/4"? Gimme a break. Put it all in decimals and even *I* can do the math!

The general contractor I worked for says that we can never switch because everything is based on a 2x4. *sigh* Forget the fact that a 2x4 today measures about 1-1/2" x 3-1/2".

TonyPSchaefer · May 8, 2006

<div class='quotetop'>QUOTE(kirbinster @ May 8 2006, 02:21 PM) [snapback]251622[/snapback]</div>

Seems to me there are a hell of a lot more important things to do in this world than invert a fraction. What the heck difference does it make which term in a ratio is the numerator or the denominator? Mile per gallon is the same as gallons per mile - just the inverse ratio, but it tells you the exact same thing.[/b]
Click to expand...

I think the point is that there's a greater sense of responsibility. Here are a few examples of shirking responsibility that see at work on a regular basis:
1. The programming code was incorrect vs. I failed to check the code.
2. The hardware was incorrectly configured vs. I wired it backwards.
3. The DHCP server was handing out the wrong IPs vs. I was in charge of setting up the server.

Like so many others, I coasted through college earning and spending money. Like so many others, I spent more than I earned because I didn't have a frame of reference for the things I purchased. Then it occurred to me: it's not just a question of how much I purchased, it's a question of how many hours of my life I had to work to afford that thing. At the time, I was earning $15/hour. When I wanted a pair of jeans, I took $30 and converted it to 2 hours. When I was looking for apartments, I calculated how many hours of the month I had to work just for rent. The result was that I valued my things much more knowing that there was not only a dollar amount but a personal investment involved.

I had a programmer friend who wrote a tiny little app. He used this app during meetings. It took the annual salaries of everyone in the room and converted it to a cost-per-minute and projected it on the projection display, always on top even of PowerPoint. Before the meeting, everyone would come up and privately enter their annual salary. As the meeting progressed, the dollar value in the bottom-right corner of the display ticked away, often by thousands of dollars at a time. Have you ever experienced a non-productive meeting because the VPs are busy BSing when they should be making decisions. Let me tell you, I was in those meetings and equally as frustrated. When my friend started saying things like, "let's take $10,000 and discuss this" or "why don't we take a $50,000 break" decisions were made considerably faster, the sidebar discussions went down and the meetings always ended on time. It was the ownership and having the monetary value of the time of all the people showed to them that made the difference.

I think that it's too easy to take something like Miles per Gallon and ignore it. After all, what a mile to people? What's a gallon to people? And when you ask someone how much it costs for them to drive a certain number of miles, they don't know. But when you tell them that they are consuming 1.5 gallons during their daily 20-mile, one-way drive to work, they will instinctively do the math themselves and know that it costs them almost $10 just driving to and from work every day.

EricGo · May 8, 2006

<div class='quotetop'>QUOTE(vtie @ May 8 2006, 04:07 PM) [snapback]251657[/snapback]</div>

This brings me to the major problem I currently have with my prius: why doesn't it show this number? Any other car I have seen the last 5 years shows me the distance I can travel before emptying the tank. I don't need to know the gallons left in my talk (I don't even know how to figure that one out on the prius). I don't need to know the mpg at that moment, and I definetely don't want to do that calculation while I'm driving. I just want to see a number "distance to empty tank". BTW do you know how many gallons are left in your tank? Are you able to do this calculation with your prius? Have you ever figured out that you have "one gallon left in the tank" ?
[/b]
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One gallon from the bell, when the last fuel bar begins to blink, is not a bad approximation in the summer. To be on the safe side, I'd cut that in half in cold winter.

walt · May 8, 2006

<div class='quotetop'>QUOTE(darelldd @ May 8 2006, 03:36 PM) [snapback]251635[/snapback]</div>

snip
Here in my shop I have two tools to do everything. SAE and Metric. Every try to find a metric hammer?
[/b]
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I do have a metric sledgehammer in the garage - 10 kg head. Also have some metric screwdrivers.

Frank Hudon · May 8, 2006

water freezes at 32 and boils at 212??? Wth
water freezes at 0 and boils at 100 What's so hard?

FreshAirGuy · May 8, 2006

<div class='quotetop'>QUOTE(DeadPhish @ May 8 2006, 03:14 AM) [snapback]251348[/snapback]</div>

Allow me to add this for your consideration. I am beginnng now, here, to promote in every venue and every conversation ( I sell Toyota's, emphasizing the hybrids, and own a Prius II ) that the method for comparing vehicles' fuel economy ratings should be changed to 'GPC' (Gallons per 100 mi).
GPC is not my idea although I have used a similar idea in past comparing different vehicle's fuel economy. GPC to my knowledge is first proposed as a metric for fuel economy in the most recent R&T article article comparing hybrids. It's elegant and simple. As R&T notes GPC or it's metric version is the normal way economy is measured in the rest of the world as 'liters/100 km'. Until the American public brings itself into the 20th century by adopting the metric system in daily use ( it has been, btw, the official system of measurement for the Federal Gov't since the mid 80's ) we are stuck with outdated, Middle-Ages terminology.

GPC is simply calculated by (dividing Gallons used by miles driven ) then multiplying by 100. It's the same process everyone now uses, except changing the variables ( dividing miles driven by gallons used ). So why propose a change?

Responsibility.

The difference in the two following statements is Responsibility.
'I get 47.2 mpg on average.'
'I use 2.1 gallons every 100 miles I drive'

One is almost a contest encouraging consumption. 'I can go farther than ...' The latter makes me consider what I use to get where I'm going. In addition now there is another readily available statistic which is very important at this time and likely into the future.

How much does it cost me to go 100 miles?

At 47.2 mpg it's not obvious what the cost of this drive actually is. But in using 2.1 GPC it's an easy exercise to see that it costs me about $6.30 at today's prices.

Which brings me to why is the US system of measuring fuel economy still in use whereas the rest of the world uses 'l/100 km'. We in the US have not been perceived as being as personally responsible as the rest of the world in our use of resources. MPG plays into this by making FE a theoretical game rather than a personal commitment. Marketing plays into this as well as certain numbers like '50' and '60' get promoted. One might even envision the fuel providers and the vehicle providers being on the side of maintaining the status quo, albeit for differing reasons.

Challenge: Think about fuel economy in terms of your personal responsibility in using as little as possible.

Herebelow are some easy examples:
Our ICE V6 Highlander uses 5 Gal/100 mi, 5 GPC on average. which currently is $15/100 mi ( or $2250 / 15000 mi )
My previous 4c Camry's used about 3.3 GPC. which currently is $10/100 mi ( or $1500 /15000 mi )
My current Prius uses 2.1 GPC. which currently is $6.30/100 mi ( or $945 / 15000 mi )

I sell SUV's and trucks which use on average about 6 GPC. Current cost $18/100 mi

Note also the verb in each sentence describing fuel economy.

Bob Fogarty
DeadPhish

Change can begin with as small a step as refusing to give up a seat on a bus.
[/b]
Click to expand...

The point is well taken. Nonetheless MPG is the CAFE standard and what most folks know. Cost per 100 miles is an enticing concept. Cost per mile however is down right gripping. At 45 MPG it costs 7 cents to drive a mile. At 15 MPG it costs three times as much. Since most folks don't drive 100 mile increments dropping the last step of your calculations will grab more attention. Thanks for the reminder.

vikingrob · May 8, 2006

<div class='quotetop'>QUOTE(FreshAirGuy @ May 8 2006, 10:36 PM) [snapback]251946[/snapback]</div>

The point is well taken. Nonetheless MPG is the CAFE standard and what most folks know. Cost per 100 miles is an enticing concept. Cost per mile however is down right gripping. At 45 MPG it costs 7 cents to drive a mile. At 15 MPG it costs three times as much. Since most folks don't drive 100 mile increments dropping the last step of your calculations will grab more attention. Thanks for the reminder.
[/b]
Click to expand...

But still, I am at 5.66Â¢/mi and 2.24 gal/100mi YTD.

(I made a deliberate decision to have my spreadsheet store data in kilometers and liters.)

darelldd · May 9, 2006

<div class='quotetop'>QUOTE(vikingrob @ May 8 2006, 08:59 PM) [snapback]251961[/snapback]</div>

(I made a deliberate decision to have my spreadsheet store data in kilometers and liters.)
[/b]
Click to expand...

Just to piss off evil Americans, right?

A new metric for fuel economy

DeadPhish Senior Member

vtie New Member

darelldd Prius is our Gas Guzzler

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TheForce Stop War! Lets Rave! Make Love!

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A new metric for fuel economy

DeadPhish Senior Member

vtie New Member

darelldd Prius is our Gas Guzzler

jbarnhart New Member

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kirbinster Member

Tempus Senior Member

darelldd Prius is our Gas Guzzler

TheForce Stop War! Lets Rave! Make Love!

darelldd Prius is our Gas Guzzler

nerfer A young senior member

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