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EPA Issues New MPG Estimate Methods; Estimates Will Likely Drop an Average 8%-12%

12 December 2006

The new EPA fuel economy sticker. Click to enlarge.

EPA has issued its final rule on new methods to determine the miles per gallon (MPG) estimates that appear on new vehicle window stickers. The new standards will take effect for model year 2008 vehicles, some of which may be available for sale as soon as next month. EPA proposed the changes in January 2006. (Earlier post.)

Compared to today’s estimates, the city mpg estimates for the manufacturers of most vehicles will drop by about 12% on average, and by as much as 30% for some vehicles. The highway mpg estimates will drop on average by about 8%, and by as much as 25% for some vehicles.

The decreased fuel economy, the EPA took pains to point out, is not a result of a change by the automakers, but in the agency’s methodology for estimating performance.

In vehicles that achieve generally better fuel economy, such as gasoline-electric hybrid vehicles, new city estimates will be about 20 to 30% lower than today’s labels, and new highway estimates will be 10 to 20% lower, according to the EPA.

The nature of current hybrid technology—the addition of a battery as a second source of on-board power, sophisticated control systems, and sometimes a smaller engine—makes a hybrid’s fuel economy more sensitive to certain factors, such as colder weather and air conditioning use.

EPA’s new methods bring MPG estimates closer to consumers’ actual fuel use by including factors such as high speeds, aggressive accelerations, air conditioning use and driving in cold temperatures.

Currently, EPA relies on data from two laboratory tests to determine the city and highway fuel economy estimates. The test methods for calculating these estimates were last revised in 1984, when the fuel economy derived from the two tests were adjusted downward—10% for city and 22% for highway—to more accurately reflect driving styles and conditions.

The city and highway tests are currently performed under mild climate conditions (75° F) and include acceleration rates and driving speeds that EPA believes are generally lower than those used by drivers in the real world. Neither test is run while using accessories, such as air conditioning. The highway test has a top speed of 60 miles per hour, and an average speed of only 48 miles per hour.

Since the mid-1990s, EPA's emissions certification program has required the use of three additional tests which capture a much broader range of real-world driving conditions, including high-speed, fast-acceleration driving, the use of air conditioning, and colder temperature operation (20° F). These conditions affect not only the amount of air pollutants a vehicle emits, but also a vehicle’s fuel economy. However, these tests were not required to measure fuel economy.

Model year 2008 vehicles will be the first to receive the new MPG estimates. Currently, EPA relies on data from two laboratory tests to determine the city and highway fuel economy estimates. The test methods for calculating these estimates were last revised in 1984.

To more clearly convey fuel economy information to consumers, EPA is also enhancing the design and content of the window sticker. The new label will allow consumers to make more informed decisions when comparing the fuel economy of new vehicles. EPA will continue to work with the auto industry, dealers, and other stakeholders, such as the American Automobile Association (AAA), to further educate drivers about all the changes included in the final rule.

In addition to better fuel economy estimates, for the first time, EPA will be requiring fuel economy labeling of medium-duty vehicles, which are between 8,500 and 10,000 lbs., including large sport-utility vehicles and vans. Manufacturers will be required to post fuel economy labels on these vehicles beginning with the 2011 model year.

EPA’s new rule has no impact on the CAFE program, which is administered by DOT’s National Highway Traffic and Safety Administration (NHTSA). CAFE is the required average fuel economy for a vehicle manufacturer’s entire fleet of passenger cars and light trucks manufactured for sale in the United States for each model year. There are separate regulations concerning the test methods and procedures to determine the fuel economy values under the CAFE program.


December 12, 2006 in Fuel Efficiency | Permalink | Comments (20) | TrackBack (0)


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Somehow I don’t I feel that good about these new revisions.

When I used to buy a car (my next one will be a PHEV), I looked at the relative mpg ratings, and considered them more like “best case”.

Now, they will tend to make all cars, with large or small gas engines, show a smaller difference in mpg? A larger gasoline engine car with more aggressive driving, air on high, etc., will “suffer” less loss in mpg than a car with a smaller engine. I don’t drive aggressively or use the air aggressively, but that won’t show up on the ratings?

If the new testing tends to converge mpg ratings, then there is less incentive to sacrifice and get that higher mileage car.

Also, many Prius drivers consistently get better than EPA ratings, by driving conservatively, and smartly. Go to a Prius forum and you will see someone complain that they don’t get near the EPA ratings. That comment will be followed by many people jumping in to give suggestions on how to drive the car smarter and beat the EPA.
This capability exists in some hybrids, but, I’m afraid, won’t show up in the new ratings, which will discourage people from paying extra to get a hybrid.

I hope I’m off on the mindset of the American car buyer.

The best "real world" mileage that my '05 Corolla gets has been 36 combined, with 33-34 more typical. My Honda Reflex scooter gets 63-67.

It's unfortunate that this won't impact CAFE. Without that, I'm not sure how much good this will do. Hopefully people will realize how bad their cars really are and buy more fuel efficient ones.
On the other hand, some of us see it as a challenge to "beat the EPA" by driving in a fuel efficient manner (like we should). This is possible with most cars in moderate temps if you drive carefully and keep tires inflated properly (my Prius got over 55 mpg on several tanks this summer, and some people can do it on a regular basis). Since the EPA estimates will become easy to beat, this may take away some of the incentive to drive efficiently.

Including the 8500 to 10000 lb vehicles is a step in the right direction, although I'm guessing that won't affect if they only closed that E85 MPG loophole. It's big enough to drive gas guzzling SUV right through CAFE and into the garages of americans.

George K:

You have a good point. A fair and effective mpg rating system should consider the driver aggressivity, driving conditions, car loading etc. There is no such thing as an automated average, covering all extremes, except with historical data.

One may wonder what was the exact role of the current gaz guzzler manufacturers (not to mention GM-Ford-Chrysler) in the selection of the factors used to come up with the new rating system.

Organisations like the AAA and CAA could come out with a better weighted rating system.

I think the lower MPG will certainly affect the sales of hybrids, however, I do not think the pool of potential buyers would shrink all that much...

For those who have already made up their minds against hybrids, this will only reinforce the mindset. For those who do not want to take advantage of the potentials of hybrid's flexibility, and more concern about nickels and dimes at the pump, then the lower MPG ratings will just be the final nail in the coffin anyways.

Even when there is a potential for high gas prices in the near future, people are still buying gas guzzlers and high-horsepower toys today. The new EPA numbers will only encourage those who cared little about MPG to buy what they would have bought anyways.

In a way, maybe these new standards will help hybrids in the long run. Naysayers will no longer be able to exaggerate about hybrids. People can finally focus more on what it takes to save gas, and less about what could be the "real world" numbers for model X.

It's about time. Current MPG ratings are a joke.

One may wonder what was the exact role of the current gaz guzzler manufacturers
The net effect is to lower the rating of hybrids relative to gas guzzlers.
Do you think Detroit has some influence in Washington [/sarcasm]

"for the first time, EPA will be requiring fuel economy labeling of medium-duty vehicles, which are between 8,500 and 10,000 lbs., including large sport-utility vehicles and vans. Manufacturers will be required to post fuel economy labels on these vehicles beginning with the 2011 model year."

We only have to wait 4 more years for the mega-guzzlers to display their fuelish estimates!

The Auto media (magazines, websites, TV shows, etc) could assist. They get new vehicles anyway, and they can put it through its paces over a year/10-30K mi, and a plethora of conditions, and driving styles. Additionally, their reputation is the key to their success/livelihood, and sane editors/writer/contributors will not besmirch it.

_3 driver profiles (aggressive, moderate, conservative-most hybrid drivers)
_5 seasons (Canadian winter, winter, spring/autumn, summer, and tropical/desert summer)
_Various types of trips (errands, commuting, weekend getaway, etc.)
_Variable loading (passenger/cargo)
_Diverse traffic/road conditions

Auto owners can help by participating in detailed surveys.

Finally EPA estimates will include Air Conditioning in the estimate. Right now manufacturers have no incentive to make more efficient AC units in cars. While large vehicles will show smaller decreases in mpg then smaller cars they will be greatly effected at highway speeds as the test is done at higher speeds and smaller cars are generally much more aero-dynamic.

This is good news. As has been observed, the current EPA stickers are joke, except for those on hybrids which are a fraud. I am glad Consumers Union blew the whistle. Truth is important, so more accurate labling is a good thing, and all those who endevour to justify misinformation for the "greater good" are IMHO hindering collective action toward environmental protection.

With the 8500-10000lb trucks being rated I wouldn't be surprised if we saw an increase in heavy duty truck sales. We have a Dodge Ram 2500 diesel that gets about 20mpg, but we traded a 12mpg 1500 series for it. We wouldn't have even bought the gasser in the first place if the diesel had an advertised fuel mileage.

why not do tests for new models to provide an estimate, then actually collect real data from real cars and use that to provide numbers once a model has been out for a year or two?

all vehicles already have on-board diagnostics that could easily keep track of fuel use and miles travelled. it'd just be a matter of collecting the data and using it for the stickers.

so you'd have three numbers, tested city, tested highway, and observed average.

that way, nobody could complain.

EPA is right to update the testing procedures to more accurately reflect average driver behavior - your own mileage will still vary. There will be a period of consumer confusion as the old and the new metrics cannot be compared directly. It would be sensible for EPA to clearly identify numbers derived using the new metric as MPG-new or some such.

For a transition period of 3-5 years, EPA should also continue to publish the numbers based on the old metric on the internet. This would help buyers compare the fuel economy of used cars to new ones. It would also help consumers get a feel for how to interpret the new metric - it is common practice to reduce the old one by ~15% to get a "real-world" number when crunching the numbers in preparation for sales negotiations.

However, it is indeed silly to use one set of MPG numbers for the stickers seen in showrooms and another to compute CAFE, this is an area the incoming Congress may wish to clean up. As a baseline, someone should calculate the impact that applying the new metric to CAFE and the gas guzzler tax would have on the viability of US automakers (incl. foreign transplants).

It would actually be legitimate practice to actually LOWER those limits and tax rates initially to avoid a severe step change in the economic burden on the industry. After that, the limits should either be raised in a predictable pattern. One alternative would be to jettison CAFE and the gas guzzler tax altogether and simply increase the fuel tax rates, with compensating changes to the income tax burden for low earners.

The important number is the amount of gallons one uses per year not the gas mileage. The existing fleet gets just over 17mpg and it will take years to bring this number up to a reasonable level regardless of innovations or changed buying habits for new cars. We need a form of cap and trade for gasoline consumption.

Having said that, I wonder if these numbers will account for the fact that hybrids with engine shut off will be advantageous in stop and go, bumper to bumper traffic jam type traffic. People who commute in in crowded conditions need to take that into account when making purchasing decisions.

I am also hearing that hybrids' highway gas mileage will be reduced as much as 20%. I find this disturbing since I can easily exceed the EPA estimates for highway mileage even when traveling faster than the EPA parameters.

EPA should not give out a number for city and one number for highway. They should stick to a range. I know they have a range now but people focus on that one number. That is simply absurd as no one number can accurately describe expected gas mileage.

Isnt it time to get off this treadmill(dynamometer)anyway? Real-time data on engine and emissions parameters may ultimately lead to improved software as well as reliable EPA/CAFE numbers.
Oh and the metric system too...grams per mile is just plain silly.

And another thing…
The sticker shows combined fuel economy for this vehicle compared to all suv’s. It’s a great graphic. But it should base the base on all “light” vehicles, for example. My thinking is, on the current sticker I’d be happy to buy an suv in the middle of the pack 10 to 31, and this one gets 21.

However, I wouldn’t be quite so happy if it included all light vehicles and I see that the highest one gets, say, 55 combined, and it puts me on the low half of the chart.

The new EPA test will hurt some hybrids more then others. I am guessing that the Accord hybrid and Civic hybrid will do quite well on the new highway test. The Accord should be running in 3cyl mode. The Prius while my favorite hybrid is weak at 65mph due to its power split device. It will be interesting to see how it turns out.

It should have always been the goal to produce numbers that are as close as possible to real world.

“numbers that are as close as possible to real world”

SJC, I agree with you. It’s just that the EPA’s real world seems to include the aggressive driver, but leaves out the conservative driver. At the Hybridfest 2006 open road mpg rally, I was one of 3 people who achieved over 99.9 mpg in my 2005 stock Prius (with my wife in the car) .
I don’t think that doubling the EPA on a non-hybrid car is possible no matter how conservative/smartly you drive.

I thought the whole idea of the EPA ratings was to encourage people to buy higher mileage cars?

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