posted
Modifying the European litres per 100kilometres to an American gallons per 100miles 15mpg translates to 6.66gallons per 100miles 18mpg translates to 5.55gallons per 100miles for a difference of 1.11gallons per 100miles Whereas 50mpg translates to 2gallons per 100miles 100mpg translates to 1gallon per 100miles for a difference of 1gallon per 100miles
Then using a bit of advertising sophistry ala "You save more money by purchasing a $500 Gucci shopping bag for $400 than by purchasing a $5 TraderJoes bag for $4" one could conclude that saving 1.11 gallons is better than saving 1 gallon.
Lyrhawn's just one of them contrarians who'd wonder how spending an extra $396 for a bag could be considered saving money.
Posts: 8501 | Registered: Jul 2001
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posted
Something is fishy in that math, like I said, I'm just not sure what it is. But I think there's something to these numbers: A 15mpg car with a 10 gallon gas tank goes 150 miles. For a 18mpg car, is goes 180 miles, for a 30 mile improvement. Nothing really to write home about is it? Same 3 mile difference in 50mpg to 53mpg takes us from 500 miles to 530 miles. Spread that between 50mpg and 100mpg and you have a 500 mile difference. Now using the 15mpg standard on those 500 miles, I just saved 33.3 gallons of gas, not 1. Even using the 50mpg standard I saved 10 gallons, not 1. I think if you're going to do a comparison by that, the mpg should be equal, not attached to the change like that, I think that's math cheating.
Besides, I think what aspectre is saying is that the savings garnered by a switch from 15 to 18 pales in comparison to the change we NEED to get is to safe sustainable levels, which probably ranges in the 50-75 range in the short term.
Posts: 21898 | Registered: Nov 2004
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posted
aspectre doesn't have a point. If we switched every 15 mpg car to 18 mpg, we would save more gas than switching the same number (not that we have anywhere near this number to begin with!) of 50 mpg cars to 100 mpg cars (not that we can make this big an improvement in fuel efficiency, practically).
It is not math cheating. It is choosing disparate ends of the range to make a simple point: if you want to save gas on a national scale, focus on the low end. Anything else is just playing around.
edit: Lyrhawn, using miles you could drive is useless. People don't drive miles they could drive, they drive approximately the same number of miles, especially considered in the aggregate. Changing the miles per gallon will not magically make them drive less or more. The only accurate comparison, if what we want to do is save gas, is gas saved given a constant amount of driving.
Posts: 15770 | Registered: Dec 2001
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posted
Forgive me, I'll admit outright that my math skills aren't generally impressive, but how are 3 miles per gallon at the lower end of the scale worth 50 at the other end? It just doesn't make sense to me, even seeing the numbers right in front of me. And I think it's suspect using an adjusting measuring bar for savings. If you look at miles driven and compare that to a flat 15mpg measuring stick, the savings are even over the scale, it's only when you slide the mpg up with it that it looks that disproportionate.
I'm not saying I wouldn't believe it if I saw a more extensive explanation, but on the surface it just looks wrong. I look at it like this: There’s a hundred gallons of gas to give out, those hundred gallons of gas mean 1,500 miles traveled for a 15mpg car. 1,800 miles traveled for a 18mpg car, 5,000 miles traveled for a 50mpg car, and a 10,000 miles traveled for a 100mpg car. Now okay, let’s say miles actually traveled is immaterial, and what really matters is gallons spent. You save 300 miles between the 15mpg car and the 18 mpg car, and in 15mpg terms, you’ve eliminated 20 gallons of gas. Going from a 15mpg car to a 50mpg car is 1,500 to 5,000 and saves 3,500 miles, and in 15mpg terms, you saved 233.3 gallons of gas. Going from 15mpg to 100mpg is a difference of 8,500 miles, and you save 566.6 gallons of gas. If I buy that 18 mpg car, to travel the same distance as a 15mpg car, I just saved 20 gallons of gas. The difference looks a lot more uniform when you put it in those terms. Explain to me why that way of thinking is wrong.
100mpg cars aren't that far off at all. I'd say we have an economically feasible one within five years. If it even takes that long.
Posts: 21898 | Registered: Nov 2004
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Americans drive approximately some X number of miles each year. No matter what the price of gas or the mileage of their cars, this number of miles will not be substantially different. This is true even down to the level of individuals, though at that level there is somewhat more fluctuation.
The question is, given how many miles Americans are going to drive, how much gas is going to be used, and what measures will save how much of that.
If the drivers in 15 mpg cars all upgraded to 18 mpg cars, they would use huge, huge amounts less gas, while upgrading those driving 50 mpg cars to 53 or even 100 mpg cars would not save as much gas (even on a per-drive basis, much less factoring in that there are many more of the former than the latter). It is always better to focus on the low end of gas mileages. Improving the gas mileage of high mpg cars by a few mpg is a rounding error in the amount of gas saved by improving the gas mileage of low mpg cars by even fewer mpg.
As for the math, (1/15 - 1/18) is greater than (1/50 - 1/100), and (1/15 - 1/18) is much, much greater than, say, (1/50 - 1/60). These are the appropriate equations, given the basic constancy of miles driven.
Posts: 15770 | Registered: Dec 2001
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posted
As for an economically feasible 100mpg car, we very well might have . . but it will still be a small minority purchasing it, and those will almost entirely be people who already have high mpg vehicles. If we persuaded the same number of people driving 15 mpg cars to switch to 18 mpg ones, we would save more gas. And there are a lot more people driving 15 mpg cars that we could persuade.
Posts: 15770 | Registered: Dec 2001
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posted
I thought this linked article to the original made it much clearer:
quote: Among them: a seemingly huge upgrade in fuel economy (say, trading a Camry for a Prius, which doubles your fuel efficiency from 30 mpg to 60 mpg) can have the same fuel-saving consequences as seemingly smaller improvements among larger vehicles (say, trading a 15-mpg SUV for one that gets 20 mpg).
Using miles per gallon, that fact just seems strange -- how can the huge jump from 30 mpg to 60 possibly have the same effect as the much smaller shift from 15 mpg to 20?
But if you use the Canadian method, there's nothing counterintuitive or confusing. Shifting from a car that burns 4 gallons every 60 miles (i.e., 15mpg) to one that burns 3 gallons over the same distance (20 mpg) saves 1 gallon of gas every 60 miles: 4-3=1. Likewise, shifting from a car that burns 2 gallons per 60 miles (i.e., 30 mpg) to one that burns 1 gallon (60 mpg) saves 1 gallon over the same distance: 2-1=1. The math is much clearer, and any apparent "paradox" disappears.
posted
I get what you are saying. I don't get how being able to drive 50 miles more on a gallon of gas is LESS of a saving than being able to drive 3 miles more on a gallon of gas. That doesn't make sense to me, no matter how many times it's repeated.
I'll take minor issue with the price of gas affecting how many miles we drive. Recent studies have shown that when prices creep much above $3 a gallon it DOES change our driving habits, just a bit, but it does, and that ripples over hundreds of millions of drivers. But for this discussion that'd really neither here nor there, and the more the price of gas hovers at $3, the less it matters.
But okay, the miles traveled isn't going to change, it's all in gallons used. In my explanation above the savings are the same throughout the spectrum. It only changes when you move the bar, but when you stick with a 15mpg spectrum throughout, the savings stay the same. Switching from 15 to 18 has the same percentage saving as switching from 15 to 100. Isn't that comparing apples to oranges to move the bar up?
quote:As for an economically feasible 100mpg car, we very well might have . . but it will still be a small minority purchasing it, and those will almost entirely be people who already have high mpg vehicles.
In the near term, yeah, you're probably right. A lot of things depend on what kind of car comes out of the Automotive X Prize contest, and whether or not Lithium Ion batteries can make PHEVs as economically feasible and viable (to what is being claimed they can do) as major car companies (well, specifically GM) would like. GM claims they'll have a PHEV that gets a 250mpg equivilant in a few years for less than 30K. It's a pretty extraordinary claim, and I've little hope that they'll be able to pull THAT off, but even a 100mpg PHEV or better for less than 30K that has mass market appeal would be impressive.
Posts: 21898 | Registered: Nov 2004
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That's how much of a greater savings there is per mile driven by improving from 15 to 18 than from 50 to 100. Do you at least follow the math?
Yes, the price of gas affects the number of miles driven, but that is small, and it doesn't matter as much to people driving high mpg cars, so if anything it will improve the comparison in favor of improvements on the low end. Mostly it doesn't matter, though.
It isn't comparing apples to oranges, it is comparing real scenarios to other real scenarios. There are high mpg cars out there. There are low mpg cars. No matter how much you might want them to, people driving 15 mpg cars are not going to switch to driving 100 mpg cars in noticeable numbers. People who are driving 50 mpg cars might switch to driving 60 mpg cars, and a few even to 100 mpg cars, but it won't matter much, because it is the many more people driving 15 mpg (or 20, or 25) cars who are using the gas, and small improvements in their efficiency will always matter more than equivalent improvements in higher efficiency cars.
If you want to reduce American gas usage, go after the people driving the low mpg cars. Any mpg improving plan that does not include going after the low mpg vehicles is a worse policy choice than one that just goes after the low mpg vehicles, just given the greater improvement ratio at the low end plus the greater number of drivers at the low end. Any plan that does not take serious steps to deal with low mpg vehicles is just looking to score some quick points by making the people who are already buying high efficiency vehicles feel even better about their mostly irrelevant improving fuel efficiency without pissing off the more numerous people in inefficient vehicles.
Posts: 15770 | Registered: Dec 2001
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posted
I get the math, I got it from the first post, it just doesn't seem like that SHOULD be true.
You don't have to school me on the policy angle, I'm already more than in favor of going after the drivers of the lower mpg cars and SUVs, have been since I started paying attention to this issue. And at the moment I too am more concerned with people driving 15mpg cars than I am with people driving 50mpg cars, though I question a lot of your statements of fact there, I don't want to get into that in this thread.
I still think my way makes a lot more sense, and I'll leave it at that, not just because my head is killing me from a combination of a bad head cold and the insanity of this math problem, but because I have to leave for work now.
Posts: 21898 | Registered: Nov 2004
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posted
I'm not entirely certain what your way is, but at least a good chunk of your math is irrelevant to a policy analysis (the parts dealing with being able to drive more using the same gallons).
The reason it should be true is because what we are comparing are not numerators in the relevant equations, but denominators. They work like fractions. Fractions work like this, and they should work like this.
Posts: 15770 | Registered: Dec 2001
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posted
How about this -- don't think of it as a car that gets 50 mpg. Think of it as a car that uses .02 gpm (gallons per mile). If you move from a .067 gpm car to a .056 gpm car, you save more gas than if you upgrade from a .02 gpm car to a .01 gpm car.
Sorry for the lack of updates on the thread lately, by the way. Things have been busy!
Posts: 3546 | Registered: Jul 2002
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posted
Lyrhawn, I think it doesn't make sense to you because the US way of presenting the data doesn't make much sense from the stand point of energy conservation.
From the standpoint of energy conservation, you need to look at how many gallons of gas it takes to go a 100 miles.
The US system makes sense is you are concerned with how far you can drive before you have to buy gas.
Posts: 12591 | Registered: Jan 2000
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posted
Given the weight of opinion, I'll have to say okay, I agree with you guys. It still feels wrong, but I'll go along with it.
Posts: 21898 | Registered: Nov 2004
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posted
For some reason, I read this thread title as "Comments on cornet". I'm clearly preoccupied by my occupation.
Posts: 1099 | Registered: Apr 2005
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quote:How about this -- don't think of it as a car that gets 50 mpg. Think of it as a car that uses .02 gpm (gallons per mile). If you move from a .067 gpm car to a .056 gpm car, you save more gas than if you upgrade from a .02 gpm car to a .01 gpm car.
That's a very good way to put it.
Posts: 16551 | Registered: Feb 2003
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posted
As a policy decision it's better to get X people to switch from 15 mpg to 18 mpg than to get X people to switch from 50 mpg to 100 mpg. Of course, it's even better to get everyone to switch to >50 mpg vehicles. Or not drive at all! *raises hand*
From the individual's point of view it can certainly make a bigger difference in utility to switch from 50 to 100 than from 15 to 18. Let's look at some numbers.
Suppose Abby and Bobby each drive 500 miles a week. Long commute, I guess. Abby drives a 15-mpg SUV and Bobby drives a 50-mpg Mini. At $3/gallon for gas, Abby saves $16.67 a week switching to an 18-mpg vehicle, while Bobby saves $15.00 a week switching to a 100-mpg vehicle. This is amortized, of course.
On the other hand, Abby normally has to fill up her 10-gallon tank 3.3 times a week. Yikes! After the switch she has to fill up nearly as often, 2.8 times a week. Meanwhile Bobby fills up once a week before switching and once every other week afterwards.
Finally, Abby's range on a single tank goes from 150 to 180, while Bobby's range goes from 500 to 1000. Bobby definitely doesn't have to worry as much about running out of gas on those long road trips, not that s/he did much in the first place.
Sure Abby's switch saves more gas (and therefore cash) than Bobby's. But arguably Bobby's switch has a much higher impact on his/her lifestyle. (Also, we're notably not factoring in the hidden costs of taking the time to fill up.)
-----
So, to sum up, lots of difference on the individual's side of things, not much when you look at collective consumption.
Posts: 1810 | Registered: Jan 1999
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posted
Given the proliferation of gas stations, I am not overly worried about the increase in welfare due to not needing to find a filling station as often.
Also, for this to have any relevance to a policy analysis one must assume a marked dichotomy between the driving habits of people currently with low mpg vehicles and those with high mpg vehicles. I do not believe there is such a marked dichotomy; at best a slight tendency.
And if the goal were to save them cash, there would be no policy; if the person could save cash overall by upgrading their car, they probably would. The goal is to reduce gasoline usage and emissions.
Posts: 15770 | Registered: Dec 2001
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posted
I wasn't sure if I got the math either until I wrote it out for myself. This assumes an equal number of cars all driving the same number of miles per day:
30 cars, 15 mpg, 10 miles per day = 300 miles total = 20 gal used per day 30 cars, 18 mpg, 10 miles per day = 300 miles total = 16.67 gal used per day 3.33 gal saved
30 cars, 50 mpg, 10 miles per day = 300 miles total = 6 gal used per day 30 cars, 100 mpg, 10 miles per day = 300 miles total = 3 gal used per day 3 gal saved
Though it looks as though this has been pretty well hashed out and didn't need more explaining, I posted it anyway.
As was already pointed out, the disproportionate amount of low mpg cars on the road only serves to exagerate the difference.
Posts: 369 | Registered: Apr 2007
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posted
Plus, it is a lot easier to move someone from a 15 mpg car to an 18 mpg car than from a 50 mpg car to a 100 mpg car .
Posts: 15770 | Registered: Dec 2001
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posted
Yeah, there are megatons of cars around that get 18mpg (or better). Good luck finding someone who has a 50mpg auto -- the Prius is the only truly mass-produced personal automobile that even makes the claim -- or finding a 100mpg car for him to switch into.
Which is why such assertions by the BobLutz's of the world that switching from a 15mpg vehicle to an 18mpg vehicle is better than Research&Development to build a more efficient means of travel is sophistry that doesn't even reach the truth level of BS.
posted
Give Lutz some credit. GM has totally turned their view of hybrids and alternative cars around in the last few years. They offer more hybrids than I think any other single car company at the moment, US or Japanese. In general US car companies have really made a turnaround in the last couple years on the subject of efficiency and hybrids, to say nothing of the growing interest and investment in PHEVs.
Posts: 21898 | Registered: Nov 2004
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posted
Of course, the same math applies for any lesser increase in mpg than 50 to 100 that's worse than 15 to 18. For instance, anyone in a 30 mpg car improving to a 35 mpg car is much less of an impact on the environment than the 15 to 18 switch.
Also, I fail to see where Lutz said anything of the kind -- in fact, in your latest link, it talks about how he is supporting research into things that are increases in efficiency in the high end, not the low end. Why do you so frequently say things contradictory to what you link, aspectre?
Posts: 15770 | Registered: Dec 2001
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The inability to consume citrate is considered a hallmark of E. coli, so this is a fascinating outcome.
Posts: 3546 | Registered: Jul 2002
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posted
Another article on lattice calculations which clarifies some of the misleading points in the other two, and vice versa.
Posts: 8501 | Registered: Jul 2001
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posted
The traps are cool. It makes me wonder what other hidden surprises could be found by amateurs perusing google earth. Sounds like a fun game, fishing for interesting aerial finds! Arr, arr.
Posts: 6246 | Registered: Aug 2004
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posted
How about driving less? How many gallons does that save? And it has the added benefit of forcing the price of gasoline to go down. All those people who tried to drive up the price by speculating on oils futures, appear to be (deservedly) losing their shirts, as the price seems to be coming down again. Should be a no-brainer. So many people have lost their jobs, and are still losing their jobs, that a very large number of people can no longer afford long, driving vacations, and in fact must limit their driving only to what is really necessary. With lower demand must come lower prices. Oil prices cannot really go back up until the economy improves, and there has been a net gain in employment for a while.
Posts: 3742 | Registered: Dec 2001
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posted
I know that graphene is mentioned earlier in this post, but I think it is cool enough to warrant repeating.
quote:Graphene is a form of carbon in which the atoms are arranged in a flat hexagon lattice like microscopic chicken wire, a single atom thick. It is not only the thinnest material in the world, but also the strongest: a sheet of it stretched over a coffee cup could support the weight of a truck bearing down on a pencil point.
quote: Among its other properties, graphene is able to conduct electricity and heat better than any other known material, and it is completely transparent. Physicists say that eventually it could rival silicon as a basis for computer chips, serve as a sensitive pollution-monitoring material, improve flat screen televisions, and enable the creation of new materials and novel tests of quantum weirdness, among other things.
quote: Dr. Geim and Dr. Novoselov first succeeded in creating flakes of graphene by peeling them off piles of graphite — the material that is in your pencil lead — using Scotch tape.
posted
Graphene isn't "completely transparent" as claimed above -- it absorbs around 3% of white light. That's actually pretty high for a single atomic layer.
Posts: 688 | Registered: Nov 2008
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