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Can U.S. Cars Meet the New 54 mpg CAFE Standards? Yes They Can

The views expressed are those of the author and are not necessarily those of Scientific American.

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purple carA new car in 2025 will go twice as far on a gallon of gasoline than a 2012 model does now, if automakers comply with new federal standards released today. The U.S. Environmental Protection Agency and the National Highway Traffic Safety Administration announced aggressive new rules to raise the fuel efficiency of cars, SUVs and pickup trucks. The Corporate Average Fuel Economy, or CAFE, standards require an automaker’s fleet of passenger vehicles to average 54.5 mpg by 2025. That number extends existing CAFE rules, which set the fleet average at 35.5 mpg for 2016, up from the current level of 27.5 mpg.

Although many car companies said earlier this year that they would support the then-proposed CAFE goals, grumbling has ensued. Automakers have resisted CAFE increases since the early 1980s, each time protesting that redesigns and technology improvements needed to reach the new targets would either be too difficult to engineer or too expensive to manufacture. An additional chorus has arisen this time around, along the lines of “Well, the companies can only achieve such a jump in efficiency if something like one-third of their fleet is made up of all-electric vehicles, to pull up the average, and the public will not buy that many electric cars.”

Both arguments are smokescreens.

Electric vehicles can certainly raise fleet averages. But changes to good ol’ gasoline-powered vehicles can achieve a great portion of the needed hike in fuel efficiency. The kicker is that many of the technology improvements have been sitting on auto industry shelves for years. And some of the improvements have already been rolled out in high-end gasoline vehicles and in standard hybrid cars.

In the past, independent engineering studies by experts at M.I.T., the University of Michigan, Argonne National Laboratory and the Natural Resources Defense Council have shown that gasoline-powered vehicles can get dramatically higher mileage by incorporating a number of incremental changes. Among them are continuously variable transmissions, which replace the inefficient gear-based transmissions cars have used for a century; starter-alternators that turn the engine off whenever the car is idling, saving gas whether the vehicle is stopped at a traffic light or rolling down a hill; direct fuel injectors that sip less gasoline than conventional fuel injectors; and regenerative braking, which converts friction at the wheels into electricity.

Changes to engines themselves, made possible by advanced, high-power electronics, can also raise fuel economy significantly. Continuous valve timing decreases the fuel that an engine needs. Cylinder deactivation halts two cylinders in a six-cylinder engine when that power is not needed—which occurs often when cars are cruising along at somewhat constant speed—thereby burning less fuel. Conversely, turbochargers can give a four-cylinder car the power of six cylinders during the relatively few moments when hard acceleration is needed, such as passing a truck on a hill, allowing larger cars to function well with smaller engines, thus getting better mileage. Vehicles can also cut weight to consume less fuel. Many of the technologies and the efficiency gains they offer, along with illustrations of how they work, are described in a detailed February 2010 Scientific American article titled Better Mileage Now.

Indeed, the mass-market mileage champ, the Toyota Prius, uses this incremental approach. Although a hefty series of batteries provides power in various circumstances, that only gets the car part way to reaching 45 or 50 mpg. The Prius has a continuously variable transmission. It uses regenerative braking. It has the stop-start feature that turns the engine off instead of idling. It also has a highly aerodynamic shape that cuts air resistance, and it travels on so-called low-rolling-resistance tires that reduce losses from road friction. Every one of these features can be incorporated into cars that run only on gasoline. Some vehicles already have some of the improvements: Honda, for example, has used continuously variable transmissions for years in many of its high-mileage cars.

Furthermore, although the new CAFE numbers sound high, they translate into less taxing goals on the road. The mileage ratings come from running cars on machinery in labs that do only a fair job of mimicking actual road conditions.

“CAFE mpg still comes from the original pair of tests that are now widely viewed as bad predictors of real-world mpg. The 34.1 mpg CAFE target for 2016 is actually equal to only 26 mpg on a window sticker. The talked-about 2025 CAFE standard — usually described as 54.5 mpg — amounts to a figure of 36 mpg combined [highway and city driving] on a window sticker,” writes Dan Edmunds, director of vehicle testing at, on the company’s detailed CAFE explainer. (The site is widely recognized as the go-to place for investigating new and used cars and automotive technology.) So if you walk into a showroom in 2025 and see car with a sticker that says it gets 36 mpg “combined,” it meets the CAFE 54.5 mpg requirement. Suddenly the new rules don’t sound so difficult to attain.

As for fuel-efficient technologies being too expensive to incorporate, the new rules (pdf) allow automakers to obtain significant tax credits for rolling them out. For consumers, EPA and the highway administration estimate that the technology needed to create cars that get 54.5 mpg—which will satisfy stiffer requirements for emitting fewer greenhouse gases—will raise the price of a car by about $2,000 in 2025. But they also estimate that car owners will earn that money back in two to three years through savings at the gas pump.


Image: 1965 Mercury, courtesy of Felix O


Mark Fischetti About the Author: Mark Fischetti is a senior editor at Scientific American who covers energy, environment and sustainability issues. Follow on Twitter @markfischetti.

The views expressed are those of the author and are not necessarily those of Scientific American.

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  1. 1. Rock LeBateau 6:32 pm 11/16/2011

    How hard can it be to hit 26mpg? European car manufacturers are churning out 70mpg diesels all the time. 26mpg in Europe and Japan is as thirsty as a dypsomaniac camel. Whose interests are being served by the thirsty cars Americans drive? Enough said!

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  2. 2. petemicus 8:40 pm 11/16/2011

    continuously variable transmissions: Horrible Technology. No power. Starter-alternators that turn the engine off whenever the car is idling, saving gas whether the vehicle is stopped at a traffic light or rolling down a hill: Unsafe Technology. Removing power from the vehicle is one less moment to react. Regenerative braking, which converts friction at the wheels into electricity: Battery cars are you serious? Pieces of junk.

    The government imposed standards has everyone driving electric go carts. Why should I be required to drive a go cart when the USA all the petroleum necessary. They are very dangerous in accidents.

    Wait is this going to turn into a global warming farcus debate again?

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  3. 3. amici 8:58 pm 11/16/2011

    A bit funny how much is US industry (as well as some of their fans) opposing those changes, like they ask for anything NEW being done.
    It was already done, decade ago.. A 10 years old Renault Laguna with 120HP engine will easily take me those 36mpg on ‘window sticker’ (or 54mpg CAFE) right now.
    Also, German VW is making new models that are switching 2 cylinders out of 4, not out of 6 as this article mentions! :)

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  4. 4. petemicus 9:20 pm 11/16/2011

    A Renault? No comment. What does VW make that can comfortably fit a family of six and tow ten thousand pounds. Granted some VW has some good technology but their cars are so small. Americans still have big families, and European cars are too expensive (VW aside) and tiny.

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  5. 5. outsidethebox 11:06 pm 11/16/2011

    It was my understanding (please correct me if I’m wrong) that we could indeed all be riding around in 50 MPG turbo diesels right now but for the fact that the EPA doesn’t want all the particulate matter from diesel exhaust in the air. One environmental good fighting another. As to getting better mileage because of CAFE standards – we better because increasing hundreds of millions of new Chinese and Indian drivers are going to be competing with us for the fuel to drive them.

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  6. 6. Dr. Strangelove 3:06 am 11/17/2011

    Yup current turbodiesel cars can do 50 MPG. With catalytic converter and filter, they can significantly reduce their toxic and particulate emissions.

    Pure electric car like Tesla Roadster can do the equivalent of 170 MPG, over 3 times higher than the hybrid Prius.

    Nothing beats the humble bicycle in energy efficiency. Gasoline contains 132 MJ of energy per gallon. The bicycle can do the equivalent of 5,000 MPG. And it’s a great workout!

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  7. 7. geojellyroll 10:40 am 11/17/2011

    The author is lacking in any meaningful engineering literacy. Worse, pushing an agenda on a scientific site.

    Hint…the technology is NOT on the shelf to produce these vehicles at an extra $2,000 a unit. Try 15 to 20 thousand extra a unit. Tax credits on lower prices means TRILLIONS in extra public debt. And no, a consumer will not save frecoup costs through better fuel efficiency…technology replacement (battery, circuitry, etc will mean multiplr MORE in maintenance.

    The best solution is what we have today. Efficient Corollas, Civics, etc. running on fossil fuels that get good mileage.

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  8. 8. oldvic 11:44 am 11/17/2011

    The average family size in the US is 3.19 people (

    How many people in the US need to tow 10000 pounds and how often do they need to do it?

    I don’t have the data, but I’ll bet that not many do.

    Choosing a car is like designing a house: you need to build a house for the biggest CONTINUOUS space requirement you’re likely to have, not for a 200 people wedding that may happen sometime in the future (or not).

    If, a few times a year, you need a big vehicle, just rent it. Why incur the higher initial cost and the bigger maintenance expenses for something you only need now and then?

    Be smart and save…

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  9. 9. byronraum 12:40 pm 11/17/2011

    With regards to the comment “Tax credits on lower prices means TRILLIONS in extra public debt.” We are already spending trillions on wars that we cannot afford, partially motivated by our need for cheap gasoline. Unfortunately, if you count in the cost of these wars, quite a bit of the cheapness seems to evaporate. I don’t know about you, but if the choice is so stark, then I would much rather put trillions into research on better technology than into fighting wars.

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  10. 10. sault 12:46 pm 11/17/2011

    Re: geogellyroll,

    Back to your old, fact-free rants, I see…

    If all those high-efficiency technologies cost $20,000 per vehicle, how come Toyota hasn’t gone broke selling the Prius, Hybrid Camry + Highlander by now? I mean, since the Prius was $23K for a number of years, they were (according to your non-existent logic) losing $10,000 PER CAR! OMG, why didn’t Wall St sell off all their Toyota shares, because that company OBVIOUSLY doesn’t know how to make money!

    Please tell me how a Prius needs more maintenance than other vehicles. Consumer Reports doesn’t seem to think so, but I guess if you’re smarter than those guys, I’ll be looking for “geogellyroll’s guide to car buying for grumpy, old curmudgeons” on newsstands any day now… I’ve had mine for 100,000 miles and 5 years and it’s still going strong. There have been so few battery failures in Priuses that there isn’t enough data to determine how long they should last. Toyota did such a good job of designing and operating their Prius batteries that many owners drive them over 300,000 miles and have very few problems. I mean, automatic transmissions tend to go out every 100K to 150K miles, but the Prius’ Planetary Gear Set NEVER disengages, NEVER shifts, NEVER grinds itself up. It just provides smooth power from 0 to how fast you wanna drive.

    Finally, Tax Credits for more efficient vehicles absolutely DO make sense. For example, since the negative health effects and property damage caused by vehicle emissions aren’t incorporated into the price of the fuel, offering a tax credit to a vehicle that doesn’t do QUITE as much damage as your average Hummer is sound policy. It’s correcting a Market Failure due to the externailities caused by fossil fuel emissions. Since you’re such a Free Market Fundamentalist, you should be familiar with basic economics before you try to step into a debate, mi amigo!

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  11. 11. sault 1:07 pm 11/17/2011

    Re petemicus:

    Ah, more fact-free rants straight from the Faux News-generated talking point machine!

    CVTs: Have you ever even driven a vehicle with CVT? I like the fact that my engine can spin up to the RPMs it needs with a CVT and just stay there cranking out power while the vehicle accelerates. All else being equal, a car with a CVT will out-accelerate a manual and an automatic because there’s no shift delay.

    It’s abundantly clear that you don’t know what a vacuum servo does or you wouldn’t be spreading your grossly mis-informed OPINION:

    Or, how in the heck does the Nissan Leaf get 5-star safety ratings when it doesn’t even HAVE an internal combustion engine? Seriously, do you guys even fire up one or two brain cells thinking through these talking points before you blindly parrot them?

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  12. 12. bigbopper 1:23 pm 11/17/2011

    The car companies should be thankful the government is forcing them to take their medicine. If they had been forced to raise mileage standards in the 90′s, they might not have needed to be bailed out in 2009. The cost of fossil fuel is only going to keep going up, and left to their own devices the car companies have a history of maximizing short-term profit at the expense of smart long-term strategizing.

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  13. 13. gmperkins 2:57 pm 11/17/2011

    The technology exists for gas engines. This new standard can be easily met.

    All the crying is because some people want the right to be able to drive tanks around on the roads, to and from work. Totally selfish on their part. I have no problem with someone who uses an efficient car to commute and a ‘gas guzzler’ like a pickup to do some sort of work or maybe go offroading. But Americans use the gas guzzlers 24/7. It amazes me how they will buy a 30k+ gas guzzler (which has costly maintenance) and then complain when gas prices go up 10 cents a gallon. Bunch of selfish, selfdeluded jerks. Lets goto war more often so you can have cheap gas. Utter morons who will trade people’s health and lives so that they can ‘do whatever they want’.

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  14. 14. denswei 7:03 pm 11/17/2011

    My 1994 Toyota Tercel routinely gets 37 mpg. According to this article, it already meets the 54.5 mpg CAFE standards!
    Acceleration is great, and it drives like a sports car (thanks to the manual transmission, and a little skill).
    I’ve followed mpg standards for a long time, and have always shopped for the most efficient (used) vehicles. After the 1st CAFE standards, mpg rose to the mid 30′s for efficient cars, and has stayed there for decades. If the standards had kept pace with available technology, all but the largest cars on the road would now be meeting the new standard.
    Not to mention gas would be cheaper if all cars met the new standard, since the price of any product is driven by demand.

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  15. 15. OnePumpChump 5:42 am 11/18/2011

    Denswei: You have never driven a sports car. (Though I’ve no doubt your car would be a blast on snow or gravel.)

    Bigbopper: The price of fossil fuels may keep trending upwards, but because of speculation-driven price spikes, we will keep seeing precipitous decreases, which make people with short memories and no imagination more inclined to buy a gas guzzler (about which they will complain during the next price spike).

    Sault: CVTs aren’t known for being able to handle big power or big torque. The fact that they aren’t suited to be in a Mustang GT means, well, they just aren’t good enough for ANYTHING. Also, many drivers can’t handle the lack of shift points for some reason, so some manufacturers impose them, defeating the purpose of a CVT.

    Petemicus: Many cars include accerometers for things like electronic stability control. You could tie the engine cutoff into that, preventing it when the car is rolling down a hill. Also, if you’ve got regenerative braking, you don’t NEED engine braking. Oh, and small cars are only dangerous because of the automotive arms race.

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  16. 16. electric38 1:40 pm 11/18/2011

    Many people are installing consumer owned rooftop solar PV for charging the EV battery. How does this affect the CAFE standard? Has CAFE shown the affect on MPG for the EV’s that are currently in use? With solar doing the charging, couldn’t the MPG be near infinite?

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  17. 17. aglindh 3:26 pm 11/18/2011

    Most of the negativity here is just baloney. I bought a Honda VX hatchback in 1994 for about $10K. It got a measured 50mpg on the road then. They stopped building them because Americans wanted more power. That same car is still running well today, 310K miles later, still getting over 40mpg measured on the hiway. Holds 5 people comfortably, has large cargo space behind — I use as small truck. It is a great car, and could be built today for under $20K. Actually is, it’s called the FIT, except that they hotted up the engine for US consumers so it only gets 40mpg (measured) on the hiway. Detune the engine a little, it will do 50mpg very nicely. As for those morons who don’t understand the clear evidence on global warming, let them vote for a moron like Perry — after all people do get the government they deserve.

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  18. 18. FOAYOCAH 3:44 pm 11/18/2011

    Why are all of these comments nit picking the details but avoiding the really big issue here? It’s like the giant elephant in the room that no one is addressing head-on. The oil companies are to blame for all of the pollution, war, greed, corruption, and stifling of technology in this industry… They are so intrenched in all our lives and have such overwhelming influence on government policy that it is the status que, business as usual. Take away their subsidies and watch how well the alternative fuel powered vehicle industry competes. GM has been saying and recently said it was imposible to create an efficient battery powered car while Tesla was driving them off the assembly line!?! Let’s talk about the real issue here, rather then debate whether technology is capable. A 1974 Honda Civc got 47MPG. Henry Ford gave his friend and neighbor Thomas Edison a Model-T Ford. Thomas Edison converted a Model-T to battery power that had a range of 100 miles (in the 1920′s!!) and then gave it as a gift to Henry Ford’s wife. New, reusable, clean, efficient technology has always been available to perfect! It has been shelved for various reasons… and not because it was some big secret that no one could figure out. Take off your corporate american blinders and debate what’s really going on here.

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  19. 19. cautiousguy 4:37 pm 11/18/2011

    It is strange and disturbing to me that automakers are still using internal combustion engines that are so inefficient, they are only able to convert 20% or so of the chemical energy in the gasoline to the mechanical energy of the drive train in the automobile. What have the automobile engineers been doing for the past century? Check out the opposed-piston, opposed-cylinder (OPOC) engine concept for one existing alternative ( What a waste to have lost all that chemical energy forever!

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  20. 20. Dredd 10:56 am 11/20/2011

    We could save two out of three barrels of oil that are now wasted during electrical generation and transportation due to the fact that the national power grid does not get very good mileage either.

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  21. 21. KevinO 6:44 pm 01/3/2012

    Existing technology can meet these new standards easily given that two decade old technology easily surpassed them. I give as evidence the 1993 Honda Civic VX — Honda called this the Ultra High Mileage version. With this car I was able to obtain an average of 66 mpg. This was mixed driving (commuting) averaged over an entire year in the Northeast. It exceeded the EPA window sticker figure which I believe was 55 mpg (Canada rated it higher).

    This car was referenced in a paper written by John Decicco and Marc Ross back in 1996 titled “Recent advances in automotive technology and the cost-effectiveness of fuel economy improvement”.

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