This never fails to fascinate me.
The chart shows how much fuel is consumed over 15,000 miles by cars of different fuel efficiencies.
The curve matters a lot. It means that from the perspective of fuel conservation, it’s not terribly important to trade in your Honda Civic to buy a Prius. But it’s hugely important to trade in your Dodge Durango for a Toyota Tacoma.
I’ll use some rough numbers to illustrate. You trade in your Civic, which averages about 32 miles per gallon, and buy a Prius, which gets a whopping 47 mpg. You’ve bumped up by 15 miles per gallon—a big deal, right?
Sort of. Over the next 15,000 miles of driving, you’ll have reduced your fuel consumption by 150 gallons. That’s fine. But consider what happens when you upgrade your SUV. That’s where the real action is.
You swap out your Dodge Durango (16 mpg on average) for a Toyota Tacoma (23 mpg). It’s an upgrade of just 7 miles per gallon. It seems tiny. But consider that over the next 15,000 miles, you will have saved 285 gallons of fuel—nearly double what your fuel-sipping neighbor saved.
It’s a mind-bender, I know. But that’s math for you. And that’s what the chart illustrates. If we want to maximize fuel conservation, we need to concentrate on places where we can move quickly down the steep part of the curve. Once we’ve gotten down to the corner—around 25 or 30 miles per gallon—we won’t get nearly the payoff from efficiency improvements.
Incidentally, this matters a lot for climate policy too. Each gallon of fuel burned translates directly into about 20 pounds of carbon-dioxide in the atmosophere. So the curve applies equally to fuel economy and global warming.
Okay, enough pedantry. Here are the take-away lessons:
- To reduce fuel use, our public policies should focus on small upgrades to the least efficient vehicles. It’s less important to tinker at the upper end. The biggest gains are at the low end—and small improvements make an enormous difference.
- The U.S. should take a cue from Canada. We should talk about “gallons per mile,” not “miles per gallon.” (North of the border, of course, it’s litres per kilometre.) “Gallons per mile” makes it much, much easier to see where the problem lies—at the low end.
Clark has looked at this phenomenon before. You can find his insights here, here, and most importantly, here.
Clark Williams-Derry
Obviously, a switch from a Durango to a Prius would be even better. But that doesn’t undermine the fundamental point—small mpg improvements at the low end can yield bigger fuel savings than bigger improvements at the high end.
sf
We really need a 55 mile per hour speed limit. Then people would be more willing to buy underpowered vehicles, as well as light weight vehicles with less than optimum crash test results. My camry 4, not exactly a hot car, can cruise all day at 85. I got a ticket once because I just didn’t have the sensation of speed. We don’t need that kind of performance.
markopolo1
Why would we make policies asking people to drive differently instead of policies that ask people to drive less?
SirKulat
Eric, I’m guessing public safety is not your forte. Local and small business is unimportant. Transit? Big deal. Walking and bicycling? Eh. The “electric propulsion” of a Pruis-type drivetrain is a significant “SAFETY” feature. Accident rates, including DEATHS could be reduced by 20% with electric propulsion. When a Prius adds a battery pack and converts to a Plug-in Hybrid (PHEV), its battery operation is limited to 10-20 miles, meaning: an economic incentive is created to drive shorter distances that support local economies and small business. In time, more destination become accessable without having to drive. Walking, bicycling and mass transit become more commonly viable travel options.Eric, are you being paid off by GM or what? I’m sick of psuedo-environmentalists like you.
Eric de Place
Merry Christmas to you too, SirKulat. Look, there may be plenty of reasons to be SUV-averse, but this post is specifically about *fuel consumption*—and what appear to be misplaced policy priorites to conserve fuel. That’s why I said: “It means that from the perspective of fuel conservation…”And:”If we want to maximize fuel conservation…”And:”To reduce fuel use…”And in the follow-up post you may have seen, I actually recommend outlawing vehicles below 18 mpg. But whatever. In any case, if you think GM is interested in paying me off—for encouraging people to switch to Toyotas?!—please have them send a check to the office.
SirKulat
Look, Eric. YOU made a direct challenge against the Prius Hybrid by claiming greater success can be had by modest improvement to standard drive train technologies employed in SUVs. Screw you. I back up my complaint, (SAFETY, small business economics, walking, bicycling and mass transit), but this goes over your pointy little head. These are fuel/energy economy measures achievable with Hybrid technology that go far beyond modest fuel mileage improvements for SUVs. The Plug-in Hybrid can effectively achieve 500+ mpg, but only when their daily use is limited. How bad does it have to get before you realize there’s too many goddamn cars, no matter their good or bad fuel mileage, driving too far for too many purposes? You just don’t get it.
Eric de Place
Listen, I hate to break it to you, but it’s a mathematical fact that you conserve more fuel switching from a 15 to 18 mpg vehicle than you do switching from a 50 to 100 mpg vehicle. (Assuming both vehicles are driven the same amount.) In fact, I just ran the numbers and, assuming the same miles driven, you save more fuel switching from a 13 to 17 mpg car than switching from a 50 to 500 mpg car!!! No kidding—you can do the math yourself. The super-duper fuel economy achievements of next-gen vehicles are great, but when it comes to conserving fuel (and reducing carbon) they’re not nearly as important as making small upgrades at the bottom end of the fleet. They don’t even come close. BTW, I also think folks should drive a lot less. And I’m guessing you don’t know me (or my work), because I’ve spent the last 6+ years arguing for safer streets, local economies, bicycling & walking, and on and on. So here’s my advice to you: drink some eggnog, chill out, and take a look around the website—you may find some stuff you like.
forestsareyourfriends
Eric,I feel my problem is with the title, “How SUVs Can Save the Climate”, which encompasses everything that still needs to change with the mainstream enviro movement. SUVs won’t save the climate. Sexy groovy cars won’t save the climate. Hybrids won’t save the climate. Not even close. Personal fuel use when compared to government and industry is small potatoes. CO2 from personal car use is a small piece of the pie. Personal change doesn’t equal social change. So everyone who has an SUV switches to a more fuel efficent one. How does that save the climate? How does it expedite the switch to a sane and sustainable way of living? With how dire the outlook is, how far will this take us? Or will it continue to keep us bound to a culture and lifeway that is killing the planet? Its a false hope. Sure, we need it all, so yea upgrading the fuel efficencies of SUV’s is an alright thing. Really they need to go. But its an inch in the right direction, and nothing more than that. There are so many false solutions flying out there and simplistic false hopes, especially when it comes to issues around climate change. If only it were that easy. Its this conflation of improvement with solution, that one is thus inclusive of the other. Its like all the emails that I get telling me if i have a different light bulb i am helping save the climate. Efficency does not equal sustainability. Efficency does not equal solution. If I put a tiny bandaid on an open gash I did not find the solution to the problem, i did not necessarily even work towards making the situation better. How many more false hopes and solutions are going to be held onto before its realized its too late?I’m fine and supportive of the work that you’ve been doing. But call it for what it is.-adam
Eric de Place
forestsareyourfriends,I don’t think SUVs are going to “save the climate.” Sometimes I use tongue-in-cheek titles for blog posts to pique interest. So I sure hope nobody thinks I seriously believe we’re going to be rescued by a fleet of Toyota Tacomas!But there is a serious point too. Maybe the best thing we can do today for the climate is something that we already know how to do: upgrade efficiency at the bottom end of the fleet. Let’s not wait for r and future Freedomcars—they won’t help much anyway—the big fuel savings are within reach right this moment.
SirKulat
I don’t argue the threat of global warming as much as its solutions. Reducing vehicle emissions is less important than changing the way we live. Eric argues unconvincingly that a miniscule mileage improvement of 13-to-17mpg reduces GHG more than 50-to-500mpg, not as much an improvement as 13-to-500mpg and beside the point. The automobile is a transportation monopoly and thus a legally arguable constitutional inequity. The only way a Plug-in Hybrid vehicle (small like a Prius or large like a GM Suburban) can achieve 100+mpg is to reduce their average daily driving distance (on limited battery power) to a point where more destinations become accessable without having to drive. Eric sides with automobile interests and corporat america. Seattlers are like that. Too much Canadian dope.
metalbot
Sirkulat:- you fail at math (correct math is not “unconvincing”.)- you fail at reading (It’s not “beside the point”, it’s the whole point his post makes.)- you fail at debating (antagonizing like-minded folks is not how you win an argument.)- you fail at being a nice guy (oversweeping generalizations and insults? You kiss trees with that mouth?)The author makes a simple point about gas mileage that has certainly escaped many commoners, myself included.That’s all. If you consider it siding with evil oil lobbies to point that out, you have some issues you need to work out. Preferably in private.
skoot_in_uk
Well…I’ve got a small car but it’s quick and does about 20 mpg. Of course this depends how I drive it. If I drove conservatively then I could probably get more miles out of a gallon. But I really don’t give a rats ass about the environment and I like driving fast so I don’t think that things will change in my driving.
michaelw256
“…assuming both vehicles are driven the same amount…”But they will not be. The argument depends on the miles driven being fixed and that the amount we drive not being influenced by the price of gasoline. At lower prices I assume (correctly, I think) that most people will take Sunday drives and other pleasure drives more frequently. At higher prices, people will plan trips more carefully and drive less.One reason to buy a high fuel efficiency car is to go more places for less or the same amount of money. For me, going where I want, when I want is the whole reason to have a car.
morrison_jay
How about going from a Lexus SUV to a Toyota Prius? In 2005 I dropped my SUV (16 or 17 mpg) and got the Prius (43 to 45 mpg).The simple fact is that none us of really need a huge SUV. We have a family of 4 and the Prius could easily handle a 3rd child. It has room for 5 and a huge trunk for groceries or whatever we need to haul around.For 95% of us, the SUV is a waste of space and gasoline. There are some businesses that have a need for a truck, but the bulk of drivers are really buying more space than they need.The simple physics dictate that moving a 5,000 pound vehicle is going to use up a bunch of gasoline or diesel. It is much easier to move a 2,500 to 3,000 pound vehicle.We need higher sales taxes and vehicle registration fees on a sliding scale based on the vehicle weight. 20% sales tax for SUVs. 0% sales tax for a vehicle that gets 40+ mpg.
morrison_jay
Forget about going to 50 mpg or using gasoline at all. We need to just goto electric vehicles and an electric grid that is dominated by nuclear, wind, solar, hydro and geothermal.That is the only chance we have of dealing with the issues of oil and climate.
SirKulat
The issue needing to be worked out, Metalbutthead, has to do with Eric dePlace’s ignorance and ego. Eric could have admitted that a miniscule mileage improvement for SUVs will do little to curb global warming, little to improve US standards of living, little to improve vehicular safety standards, little to support localism, etc. But noooo, Eric had to get on his high horse, fix his hair and stroke his wounded ego after my legitimate complaint. Boo frickin hoo. Electric motor drive is opposed by automobile-related interests, including electricity utilities. When Eric dePlace diminishes the value of hybrid-electric technology, corporat america applauds.
Elisa Murray
A quick warning: Our policy is that while our blog thrives on free speech, if a commenter begins to openly insult other commenters or contributors, we will remove comments.
SirKulat
I’ll try to be civil where I must dissent, but if this censorship warning becomes evidence of shooting-the-messenger, sightline loses credibility.
smthng_fishy
While Eric is correct that more gasoline is “saved” by increasing the mpg of a low-efficiency vehicle a small amount than increasing the mpg of a high-efficiency vehicle a large amount, I think an important point is being missed. By emphasizing the “fuel saved”, we are ignoring the “fuel used” component. Those that are driving gas guzzlers are using a disproportionately large amount of fuel, compared to those driving gas-sippers. The fuel-saved argument can be interpreted to mean that moving from 13 to 17 mpg is “greener” than improving from 40 to 45 mpg (although I don’t believe that Eric intended it to be). However, when one compares the savings (and fuel used) by replacing a vehicle that gets 13 mpg (1153 gallons used per year, 15000 miles driven) with one that gets 17 mpg (882 gallons used, 271 saved) or one that gets 45 mpg (333 gallons used, 820 gallons saved over 13 mpg, 550 gallons saved over the vehicle with 17 mpg), the fuel efficient vehicle is a clear winner. The question should not be about what vehicle is being replaced, but rather what it is being replaced with. It is clear that we are not going to solve the problems created, or contributed to, by automobiles (greenhouse gases and other pollutants, dependence on foreign oil, etc) by improving the fuel efficiency of SUVs by a small amount. A better approach would be to convince the general public to move away from them entirely in favor of truly fuel efficient vehicles, and to combine that with efforts to reduce the miles driven.
tomhopper
While the switch from 15 to 18 may save more gas, I think this is actually a good example of begging the question.The U.S., with 5% of the world’s population, consumes around 25% of the world’s petroleum, about half of that in the form of gasoline and diesel for vehicles. If everyone used gasoline like Americans do, there wouldn’t be enough to go around. In addition, we are all now aware that petroleum is being consumed much faster than it is produced (via natural processes). At current rates of consumption petroleum will probably be too expensive to use for cheap transportation within thirty years.The real question is not “which improvement saves more total gasoline,” but “how much gasoline can we afford to burn?” For instance, if we were to set a target of consumption commiserate with our population, reducing our consumption to 5% of the world’s total consumption, we would need vehicles with average fuel economies of around 130 mpg. If we want to double the length of time that we can afford to drive oil-powered vehicles, we need to double the fuel efficiency to about 45 mpg (assuming similar reductions in other oil-consuming industries).
Morgan Ahouse
The main thing I like about Eric’s post is that it provides us another argumentative tool to influence a part of our society that has thus far been less interested in environmental issues—those who drive low mileage vehicles. I’m not claiming that this single action is enough, but in order to properly address climate change (eventually), in order to get the legislation and the cultural shifts we envision necessary, we will have to engage and win the support of almost every nook and cranny in our population.
captbob
I’m guessing that most of the folks in this thread live in urban/semi-urban areas. This is an interesting post to me because I live in Montana, part of the vast middle in the US whose population drives big, older rigs because a) they actually have to haul something a lot/most of the time, b) incomes are relatively low so folks can’t be swapping vehicles whenever they feel like it, and c) a lot of folks buy their vehicles with cash, which makes the swapping out even less attractive. More importantly, a lot of folks live quite a distance from where they do business, or shop. Using a bike to drive 40 miles to get your groceries just doesn’t work, especially in the winter (8 months of the year). Electrics might make sense, eventually, when they can haul 3/4 ton of hay in -20 degree weather, but until then, we’re going to continue to use bigger rigs. As an owner of a bigger rig (among other vehicles, including bikes), I’m kind of suprised at the lack of information there is on how to improve gas milage with larger vehicles. I’ve got a 1/2 ton that gets 17.3 mpg regardless of whether I’m towing a trailer, am empty, driving 55 or driving 70 (my aerodynamic profile makes it pretty inefficient anywhere past 40 mph). This is based on 8 years of gas consumption records. The main thing that causes mpg to drop is running in 4WD (which happens Nov-April/May because of ice) and winter cold (where it drops to around 15 mpg). I’d like nothing better than to improve this average to 20 or 22 mpg, but so far, haven’t been able to find any useful resources on how to accomplish this. We don’t use the A/C, so what would be the impact of removing the A/C compressor on weight? When we need to change tires, what is the impact of switching to lighter wheels and tires? How about some options for carrying around the full-sized spare tire everywhere (@80 lbs or so)? What would be the impact of replacing select engine parts on gas milage (or even changing fuel injection ratios, replacing pistons/valves with lighter, more expensive yet efficient versions). Finally, I believe I read somewhere that improving the efficiency of older vehicles creates a far better carbon footprint than purchasing a newer vehicle (something I don’t often see recognized in these kinds of conversations). I thought this post was useful. Now, where does one find out how to make the improvements to move from 13 to 17mpg, or 17 to 20mpg (that are based on fact, not wishes).
gster
Right now we allow car companies to balance low efficiency vehicles with high efficiency cars. Eric’s excellent article shows why this doesn’t sound as good as one might think. It takes a lot of hybrids to make up for one hummer!
Don
And Sirkulat loses this argument
Steven Sidman
Good argument, application of Pareto Principle and so forth (focus on the 20% that matters), but maybe doesn’t go far enough. Specifically, are there numbers that break down the current US car demographic by MPG? How many SUVs would have to convert over to achieve a meaningful effect, such as lowering gas demand by some number?And what about trucks and buses? I know, the metric there is different – not just how far can you go, but how much are you carrying. Still, with big rigs and busss getting 4-5 MPG, any improvement would likely have big effects on total consumption.Are there no hybrid trucks? Oh, wait a minute – there are, only they have steel wheels and they’re called diesel electric locomotives…