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Paper suggests it's more useful to express fuel economy in gallons per mile. (http://www.cnn.com/2008/TECH/06/20/fuelefficiency.ap/index.html)

http://www.cleanmpg.com/photos/data/501/Pumping_Gas.jpgAP - June 22, 2008

This will highlight improvements in gas guzzlers instead of gas mizers, but could it encourage complacency at some point? - Ed

Washington - With the price topping $4-a-gallon everybody wants to save gas, but depending on those miles-per-gallon ratings may be misleading.

Strange as it may sound, rating cars at gallons-per-mile may be more useful, say a pair of university researchers.

Richard Larrick and Jack Soll got to discussing fuel efficiency while carpooling to work at Duke University's Fuqua School of Business.

The professors study how people perceive things and decided to look into the auto efficiency ratings and what they tell consumers....http://www.cnn.com/2008/TECH/06/20/fuelefficiency.ap/index.html

In general, I think it's a good idea.

If we went that far, maybe we should just go metric.

In general, I think it's a good idea.

If we went that far, maybe we should just go metric.

as long as there are 36 centimeters per meter. :flag:

edit**

and 1760 meters per kilometer...wow those are oximorons if i've ever seen one!

I notice theLimeyBrit (http://www.cleanmpg.com/forums/member.php?u=2779) is reading this with interest and understand since the UK is in the process of converting and it's not been an easy or in some cases popular transition.

Well from a consumption and cost standpoint it does make more sense to me for it to be gallons per mile.

Its really easy to equate how much a 20 mile trip will cost you if you know your car gets .05 Gpm. You can then say that trip is going to take about 1 gallon of gas so thats 4$ to get there.

And I thought the only country still using the imperial system was the US... :confused:

I remember when Canada switched to Metric, it certainly was not a simple and painless process.

To this day, my parents (in their 70s) still cannot think in metric.
For me (in my 40s), it's kind of a half-half situation:
I'm comfortable with kilometers and litres but up to recently was still converting to MPG (imperial not us) for fuel consumption. Now I use l/100km.
The air temperature is in celsius but the pool water's temp is in farenheit (don't ask)
My weight (as in getting on the scale) is in pounds but everything we buy at the food store in in grams/kilograms!

It quite a mess! :rolleyes: I guess it'll take at least a generation (all the ones born after the conversion to metric) before it's all standardized in our heads!

I wish we would switch to the metric system. I remember when i was in elementary school they said when you get to high school we will all be using the metric system, when i got to high school it was when your in college we will all be using the metric system. Now i am getting older and i want to tell my kid we will be using the metric system but i dont want to lie to him.

The best comparison is fuel cost per mile. The last time I gassed the Insight, fuel was $4.09 and I averaged 96.1 MPG, that makes the fuel cost per mile $0.042. My Suburban averages 11 MPG, so it cost $0.371. If you run the numbers out a little farther it cost $3718.18 to drive the Burban 10000 miles compared to $425.59 in the Insight......Louis

The best comparison is fuel cost per mile. The last time I gassed the Insight, fuel was $4.09 and I averaged 96.1 MPG, that makes the fuel cost per mile $0.042. My Suburban averages 11 MPG, so it cost $0.371. If you run the numbers out a little farther it cost $3718.18 to drive the Burban 10000 miles compared to $425.59 in the Insight......LouisThat's now a poll option.

Ultimately the answer is $ / mile..
but the issue with $ / mi is the change in gas prices.

Gal / Mile Or per 100 Mile is the next best thing for comparison - and people can usually figure in the $/gal easily ( just multiply)

with Mile per Gallon - it is hard for people to relate that to $ with only calculating in your head.

My Altima last tank was..
32 MPG
or 3.125 Gallons / 100 Mi

the latter ( factored with $4 / gal) is more telling than the former.

Steve

I voted other. The best way to express it is to just sell EV's, then we don't have to worry about MPG anymore. Then it's mpkwh vs kwhpm.

When I read the title on this, I thought of a parking spot I found at Walgreen's. I came in a little fast, so FAS'd around the lot trying to get every foot out of the speed. I found a wonderful uphill spot. Nose in, but that's no problem. Before starting the engine, I switched the ignition on, backed out coasting, made a reverse U turn and went down the driveway, out and a full city block downhill without even turning on the engine.

Bad thing is, my Scangauge got none of it. Guess it has to get some fuel flow to start it even in hybrid mode. I'm not even sure it registered on my Odometer. But it will help my gallons/week number.

I think from now on, I'll park in that space and walk across the street to McDonald's to save gas. That will prevent a circle of McDonald's and a left turn.

It's the little things that count.

I've thought in terms of gal/100 miles (rather than mpg) for many years.

What we're really talking about is minimizing fuel consumption per distance traveled, not maximizing distance per fuel consumed.

Using MPG overemphasizes the relatively minor consumption differences between FE vehicles and hides the big consumption differences between FSPs. In terms of fuel consumption, the difference between 10 mpg and 11 mpg (1 gal/100 miles) is twice as big as the difference between 40 mpg and 50 mpg (0.5 gal/100 miles).

I came to this same conclusion nearly two years ago. And I did it in my spare time, not at Duke getting government grants. Not "gallons per mile", as this is a small fraction which is hard for the average user to comprehend, but Gallons per Hundred Miles (GPHM), which can be a US analogy to Liters per 100 km, but without forcing a wholesaqle conversion to metric. And it's so simple:

100 * 1/MPG = GPHM

So for example, if you got 20 MPG, that would be (100)*(1/20)= 5 Gallons used per 100 miles driven. This would be a much more meaningful way of comparing various cars based on their fuel efficiency.

Cost per Mile (dividing price per gallon by MPG) is a much more on-the-spot way of assessing one's own vehicle, as price is a variable that changes daily (almost hourly!) without driver intervention or control. GPHM is based only on the performance of the vehicle and its driver.

While I can't post an attachment here yet, the graph of GPHM vs. MPG is a descending exponential curve. This suggests that one achieves a greater gain by making improvements in the low-efficiency region (10-5 MPG), while only getting diminishing returns in the higher-efficiency ranges (30-35 MPG & up). (Still, that doesn't stop guys like xcel from trying!)

I like litre's per 100 km and with my commute being almost exactly 100 km's it makes it really easy for me to calculate the cost of my commute.

I was able to show someone at work really simply that their 100 km commute would cost them $5 more a day in a Honda s2000 vs a Yaris. Then I showed them how me driving 80-90km/h in our Yaris vs 120 km/h that most people do around here, saved me over $2 a day.

Lpk or mpg makes the ability to attach a monetary value to FE a little easier imo.

For FSP's, I like L/100km. Seeing two vehicles, one that gets 20L/100km and the other that gets 25L/100km makes me notice much more than comparing 11.8mpg and 9.4mpg, which is the equivalent rating. I suppose gallons per mile would be pretty much the same as L/100km and just as good, but I prefer the metric version because I'm not still stuck in the 1970's like many Americans ;)

Even with my preference for L/100km, my ScanGauge is set up to show mpg. At low consumption rates, showing mpg gives much better feedback than showing L/100km. For example, 3L/100km is 78mpg, while 3.1L/100km is 75.8mpg. Running in L/100km tends to mask the effects of my driving style on fuel economy.

Miles per gallon is the simplest way. It shows how far a car should be able to go on a gallon of gas, as $ per mile is impossible with changing gas prices and the metric system is nearly impossible to convert off the top of your head.

If for example anyone says something like 3l/100km you can be damned sure I'm typing it into Google to find out what it is MPG because I otherwise don't have a chance of knowing. I'm going to guess it's about 80 MPG though?

And when someone talks about stuff in metric, it's frankly annoying.

If for example anyone says something like 3l/100km you can be damned sure I'm typing it into Google to find out what it is MPG because I otherwise don't have a chance of knowing. I'm going to guess it's about 80 MPG though?

It's very simple once you remember the conversion factor. 235 / [mpg or l/100km] = [l/100km or mpg]. For example:

3l/100km -> 235/3 = 78.3 mpg
20mpg -> 235/20 = 11.75l/100km

Using 240 instead of 235 is only about 2% off, and much easier to do mentally. In that case, 3l/100km is 80mpg, right at where you guessed.

Miles per gallon is the simplest way. It shows how far a car should be able to go on a gallon of gas, as $ per mile is impossible with changing gas prices and the metric system is nearly impossible to convert off the top of your head.

If for example anyone says something like 3l/100km you can be damned sure I'm typing it into Google to find out what it is MPG because I otherwise don't have a chance of knowing. I'm going to guess it's about 80 MPG though?

And when someone talks about stuff in metric, it's frankly annoying.

Please see the table I made for my signature. There is _almost_ a pattern so it could be easy to memorize, and you could simplify it yet a bit to get all even numbers

I hope you do not find us metricheads too annoying :(

American actually do use metric units a lot. You can't buy a fifth of whiskey at the liquor stores anymore, it's 750 ml. Our electricity is all measured in metric units, I don't even think there are Imperial units for it. With the exception of a marathon race, long distance foot racing events are all in kilometers.
There are some things that I am used to comparing in metric units, like the size of motorcycle engines. If you tell me that a motorcyle has a 45 cubic inch engine, I have to mentally convert that to 750 cc to get an idea of how it compares to all the other bikes I have owned.
On the other hand, if you tell me that a city is 200 km away, I have to mentally convert that to miles in order to get a feel of how far away that is.

Miles is actually a good unit for measuring driving distances, it's about how far you can drive in one minute.
A nautical mile is a good unit for ships because it is exactly one minute of lattitude around the earth, even hard core metric countries still navigate with nautical miles for that reason.
Farenheit is a great scale for measuring temperature because almost all of the earth's weather happens between 0 and 100 degrees F.

Really, its the way we measure speed that's backwards. We should express it seconds per mile. It makes it much easier to see the absurdity behind the fact that everybody goes over the speed limit yet almost nobody runs to their car in the parking lot.

For me I will stick to mpg. I know that I get x mpg and each gallon cost me $x.xx and my drive to work it x miles. So for me the conversion is something I am used to. The fact that I used 0.0166898148 gallons per mile on my last fill up doesn't help me at all and even knowing that I used 1.67 gallons per 100 miles isn't even that informative when every dailly trip I take no more than 25 miles. I will stick to mpg for now. Thanks!

While I can't post an attachment here yet, the graph of GPHM vs. MPG is a descending exponential curve. This suggests that one achieves a greater gain by making improvements in the low-efficiency region (10-5 MPG), while only getting diminishing returns in the higher-efficiency ranges (30-35 MPG & up). (Still, that doesn't stop guys like xcel from trying!)

I'm not disputing the greater relative gains, I'm disputing the amount of fuel still being used despite these greater gains. I'm concerned about the absolute amount of fuel being used, not so much about relative improvement, and that's where the high efficiency ranges win big.

Going from 15 MPG to 20 MPG will save 200 gallons over 12000 miles. Not bad, but it's also using 400 more gallons than something getting 60 MPG. Most often, these relative metrics seem like turd shining.

The other thing is, while using consumption / distance has value, you lose precision as efficiency gets higher. Besides, I like getting high scores. :)

Really, its the way we measure speed that's backwards. We should express it seconds per mile. It makes it much easier to see the absurdity behind the fact that everybody goes over the speed limit yet almost nobody runs to their car in the parking lot.

No, we need them in either feet per second or meters per second for our metric friends. That way when a cop gives you a ticket, they can actually tell you that you were speeding. Right now when you get a ticket for going 80 mph in a 20mph schoolzone... what if you were going 80mph for 1 minute, and then parked your car on the side of the road for the other 59 minutes? Then you speed was actually 1.3 miles per hour. Yep, it's all just a technicality but I remember one of my professors making a big deal out of it.

No, we need them in either feet per second or meters per second for our metric friends. That way when a cop gives you a ticket, they can actually tell you that you were speeding. Right now when you get a ticket for going 80 mph in a 20mph schoolzone... what if you were going 80mph for 1 minute, and then parked your car on the side of the road for the other 59 minutes? Then you speed was actually 1.3 miles per hour. Yep, it's all just a technicality but I remember one of my professors making a big deal out of it.I think feet per second is a great idea. If people really realized how many feet of ground they're covering per second, they might actually slow down for school zones and other areas where there are lots of pedestrians. 30 mph is 44 feet per second ... a typical reaction time of 1 second (assuming an average driver who's actually paying attention) means that at 30 mph you travel 3 carlengths before you even hit the brake.

No, we need them in either feet per second or meters per second for our metric friends. That way when a cop gives you a ticket, they can actually tell you that you were speeding. Right now when you get a ticket for going 80 mph in a 20mph schoolzone... what if you were going 80mph for 1 minute, and then parked your car on the side of the road for the other 59 minutes? Then you speed was actually 1.3 miles per hour. Yep, it's all just a technicality but I remember one of my professors making a big deal out of it.

The reciprocal part is what I am advocating. time per distance instead of distance per time. Have you ever gone 60 miles per hour and had someone pass you in a no-passing zone so that he could go 70 miles per hour only to turn into a driveway one mile down the road?
If instead of 60 mph, we said 60 seconds per mile and instead of 70 mph, we said 51.4 seconds per mile, then without doing any division it is easy to see that the guy who passed you only saved 8.6 seconds of his precious time by burning a lot of gas and risking a reckless driving charge and/or a serious accident.
If it takes you a minute to walk to where your car is parked, then running instead of walking might save you 30 seconds of time, saving 30 seconds of time by speeding means you would have to drive 3.5 miles at 70 mph instead of 60.
Funny how you almost never see people run to their cars unless it's raining hard even though they drive like they are headed to a fire.

Funny how you almost never see people run to their cars unless it's raining hard even though they drive like they are headed to a fire.Awesome! How true. I've never thought of it that way.