Feds Fail to Recognize Benefits of Idle-Stop Systems

May 4, 2011

Though idle-stop technology has been available on European cars for years and is projected by the EPA and NHTSA to be included on a whopping 42 percent of vehicles by 2016, there are currently only three non-hybrids offering the feature in the United States: the BMW M3, and the Porsche Cayenne and Panamera models. Unfortunately, these 2011 models using idle-stop get absolutely no boost in MPG on window stickers, or for CAFE standards, compared to 2010 models without idle-stop. This is despite the technology’s great promise to improve efficiency at a modest cost.

Idle-stop, or stop-start as it’s often called, shuts down a car’s engine completely when it isn’t needed. The engine restarts when the driver accelerates. The feature can provide fuel savings of 5-10 percent at an added cost of as little as $300.

With gas prices threatening to surpass record highs this summer, mainstream American consumers who could take advantage of the system’s cheap mileage boost are out of luck. The only vehicles offering stop-start are hybrids and luxury models priced beyond the range of the people hardest hit by rising fuel costs.

The lack of incentives for automakers to add idle-stop technology here will keep sales in North America well below Europe and Asia, according to John Gartner, a senior analyst at href="http://www.pikeresearch.com">Pike Research. “With nearly 50 models to chose from, European customers are expected to buy nearly 3 million idle-stop vehicles in 2011,” Gartner said. “American consumers would also embrace vehicles that don’t burn fuel when stopped if they had similar options.”

So why is one of the most inexpensive yet powerful fuel-saving technologies in existence not available on mainstream vehicles? Partly because the EPA and the National Highway Traffic Safety Administration don’t count it towards the official fuel economy rating of a vehicle—meaning that carmakers get no credit for the boost in their CAFE ratings or on EPA window stickers. In other words, automakers have no incentive to add idle-stop.

BMW first offered stop-start on its M3 this year, but neither its city nor highway rating improved a single MPG over the 2010 model. The Porsche Panamera and Cayenne’s fuel-economy ratings did improve, but as a result of a new engine, better aerodynamics, and standard low rolling resistance tires—not the idle-stop systems.

Blame the Test Cycle

During the EPA’s test cycle, a vehicle comes to a complete stop only once, leading to just a 0.1 to 0.2 mpg improvement in fuel economy. (Update: On the CAFE urban test cycle, the car is idle has about 19 percent of the time, or 10 percent for combined highway/city. The European test cycle has approximately twice the idle time, and those EU idles are much longer in duration, which increases the benefit. Overall, the benefit of idle-stop on the EU cycle might be about three times that on the US cycles.)

So it’s not that there is no benefit US test cycle, just not huge, and much lower than Europe. Depending on how it was implemented, the BMW and Porsche models could have receive only a 1-2 percent improvement, which may not have been enough to cause a 1 mpg change on the label. Nonetheless, the cars could have received some benefit for CAFE.

European tests include more stops—explaining why the technology is on the verge of being widespread in the EU—and the EPA has promised for several years to refine the its test procedures, but so far no announcement has been made.

The good news is that things could soon change—at least if Ford and GM’s production schedules are any indication. G.M.’s new eAssist mild hybrid powertrains and Ford’s appropriately named Auto Start-Stop system feature idle-stop technology, and both will debut by the end of next year.

Still, the failure of American regulators and carmakers to incentivize such a simple and inexpensive fuel-saving solution in time for $4 gas is a shame. Consumers are flocking to small, inexpensive vehicles like the Chevy Cruze and Ford Fiesta, which tend to get outstanding fuel-economy on the highway but are not impressive in the city—where stop-start is most useful. For the time being though, consumers looking for substantial gas savings at an affordable price may be best suited to look for a used hybrid.


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  • Anonymous

    2012 Kia Rio is said to include start-stop technology

  • Yegor

    This is reductions! The test has to be changed!

    Is there any traffic lights in USA? Hello there! Anyone can give me an answer?

    They must most definitely change the test!!!

  • NOBAMA

    the advantages for all cars to have a stop-start system go beyond better mpg. The reduction of car emissions in the city, especiallly during rush hour would plummet. The noise level at intersections would drop. The quality of life would go up for everyone accept the oily arabs…..allah !

  • John K.

    Worth repeating:

    “The only vehicles offering stop-start are hybrids and luxury models priced beyond the range of the people hardest hit by rising fuel costs.”

    and

    “Still, the failure of American regulators and carmakers to incentivize such a simple and inexpensive fuel-saving solution in time for $4 gas is a shame. Consumers are flocking to small, inexpensive vehicles like the Chevy Cruze and Ford Fiesta, which tend to get outstanding fuel-economy on the highway but are not impressive in the city—where stop-start is most useful.”

    IOW, the cars and buyers who could benefit MOST from this inexpensive technology are NOT getting it because businesses are following EPA bureaucrats’ lead. STUPID ! ! !

    Even big F-series Ford trucks would benefit in rush hour traffic.

    Haven’t those EPA bureaucrats ever had to contend w/rush hour traffic in D.C’s Beltway? (rolls eyes) Idiots!

  • Grumpy old 1

    Why don’t they just push the cars through the test and then they can claim hundreds of miles per gallon! This is not a true savings on mpg. Lets stop trying to lie to the auto public and give them what they want a test that actually shows what the M.P.G. is, and stop using all these smoke and mirrors to try and improve their tests. By now every car manufacter should be able to make a car that can gets 40 to 50 mpg. the tecnology is there but they don’t want to give up their big money makers (pickup trucks, large SUV’s). So when the auto buyers stop buying these types of vehicles maybe the auto makers will start putting out cars that get decent milage!! Where are the Plug – in- Hybrids??

  • Samie

    The logical question is why doesn’t the EPA and NHTSA count more idle-stops in CAFE testing?

    Could the testing of more idle-stops reduce fuel ratings claimed by automakers?

    So John-K you said “businesses are following EPA bureaucrats’ lead. STUPID ! ! ! ”
    Maybe it is the EPA bureaucrats’ following the car producers lead in not creating more real world testing so that consumers have inflated mileage claims……

    Don’t know if I’m right but that is the question we should be looking at…..

  • Samie

    Ok to clarify what I said, hypothetically car-manufacture claims of mileage goes down if more idle-stop tests where added. Could this negate adding idle-stop systems if it is a breakeven or net loss in EPA fuel ratings if the rating reflected a lower, more realistic fuel number even with idle-stop technology added in?

    If that is the case, the article is not looking into the right reasons for why more idle-stop testing is excluded.

    Again I would need to know if my hypothesis is correct or if a few extra idle tests would do little to hurt the outcome of the overall EPA rating.

  • VoltSkeptic

    The problem is the the EPA test is not reflecting actual driving conditions. Everybody stops their cars multiple times during their drive, at intersections, traffic jams, etc In big cities they’ll do it for minutes at a time during rush hour. The EPA tests for city driving should include more stops, as well as have a pollution scale. This way the actual benefits of idle stop technology would be evident and people could get a reminder about how much crap they put in the air. In the (fake) table below, the Prius pollutes less the expected 150p in a 100mile drive because of the idle stop

    Ford F-150 Prius Focus
    Pollution 50p 25p 0*
    Mileage 15/19 50/48 NA
    100mi Cost $20 $8 $3
    100mi Pollution 300p 130p 0*

    * – Never pollutes locally, but there will be additional Power Plant emissions if not charged at night.

  • jwishart

    Not sure what the author is talking about when he writes that “During the EPA’s test cycle, a vehicle comes to a complete stop only once…” This is incorrect, especially now that the 5-cycle methodology is used instead of just the FTP and HWFET cycles. It’s true that there are fewer stops than in the European (and Japanese) cycles (the vehicle is stopped some 18% of the time on the FTP, 0% of the time in HWFET and over 30% of the time on the European NEDC cycle), but it’s certainly not zero percent of the time.

    It remains to be seen (I am currently running a study with 7 vehicles) what kind of real-world fuel economy gains can be obtained by idle-stop systems. With actual data, the EPA may be compelled to change their dynamometer cycles.

  • FamilyGuy

    So much for the newer EPA MPG being more realistic. One stop? I can’t tell you the last time that I drove and only made one stop. Give me a break.

    This makes them look foolish.

  • jwishart

    The author makes unsubstantiated claims here:
    “BMW first offered stop-start on its M3 this year, but neither its city nor highway rating improved a single MPG over the 2010 model. The Porsche Panamera and Cayenne’s fuel-economy ratings did improve, but as a result of a new engine, better aerodynamics, and standard low rolling resistance tires—not the idle-stop systems.”

    How does he know what effect the idle-stop system had? Does he know for sure that BMW changed absolutely nothing from 2010 to the 2011 model? How does he know that the idle-stop system didn’t contribute to the Porsche vehicles’ fuel economy improvement?

  • chukchaTheGreat

    @Samie
    #1)I think the real reason why the government is so slow and unwilling to change the rules and promote fuel saving technology is because the government looses tax income when you spend less at the pump. Remember, they tax our fuel to the gills. Less fuel sold = less tax collected. It is simply not profitable for them to push the automakers for efficiency.
    #2) Think about who is winning when you’re buying a fuel efficient car? Only you do.That’s right; the rest of the gang loses i.e. feds and automakers who are in bed with the oil corporations.

    #3) The feds and the [all the] automakers never gave a damn about you and me or about efficiency or about the environment. They are driven only by profit. The only reason they even implement efficient engine technology is because of competition and constant nagging and bad press by the public. We are a big nuisance to them all. That is why every fuel saving tech that comes out takes so long for them to implement. It feels like we’re “pulling their teeth” and they reluctantly throw us some half baked, super over priced, last century tech instead of a solid and cost effective technical solutions that make sense.

    #4) There should be a law that prevents the manufacturers from selling a vehicle WITHOUT a start-stop system. This is embarrassing that automakers in the 21st century are fighting so hard NOT to install a $20 Chinese made mini clutch system for the alternator and a mod for the on-board computer (which is essentially what a start-stop system is).

  • jwishart

    The author makes unsubstantiated claims here:
    “BMW first offered stop-start on its M3 this year, but neither its city nor highway rating improved a single MPG over the 2010 model. The Porsche Panamera and Cayenne’s fuel-economy ratings did improve, but as a result of a new engine, better aerodynamics, and standard low rolling resistance tires—not the idle-stop systems.”

    How does he know what effect the idle-stop system had? Does he know for sure that BMW changed absolutely nothing from 2010 to the 2011 model? How does he know that the idle-stop system didn’t contribute to the Porsche vehicles’ fuel economy improvement?

  • chukcha

    @Samie
    #1)I think the real reason why the government is so slow and unwilling to change the rules and promote fuel saving technology is because the government looses tax income when you spend less at the pump. Remember, they tax our fuel to the gills. Less fuel sold = less tax collected. It is simply not profitable for them to push the automakers for efficiency.
    #2) Think about who is winning when you’re buying a fuel efficient car? Only you do.That’s right; the rest of the gang loses i.e. feds and automakers who are in bed with the oil corporations.

    #3) The feds and the [all the] automakers never gave a damn about you and me or about efficiency or about the environment. They are driven only by profit. The only reason they even implement efficient engine technology is because of competition and constant nagging and bad press by the public. We are a big nuisance to them all. That is why every fuel saving tech that comes out takes so long for them to implement. It feels like we’re “pulling their teeth” and they reluctantly throw us some half baked, super over priced, last century tech instead of a solid and cost effective technical solutions that make sense.

    #4) There should be a law that prevents the manufacturers from selling a vehicle WITHOUT a start-stop system. This is embarrassing that automakers in the 21st century are fighting so hard NOT to install a $20 Chinese made mini clutch system for the alternator and a mod for the on-board computer (which is essentially what a start-stop system is).

  • Shines

    Here’s the test from fueleconomy.gov (the official EPA site):
    It doesn’t translate well on this post but their tests involve 23 city stops; 5 stops with a cold engine and 5 more with a warm engine as well as high speed and running with the AC on and off. It seems much more comprehensive than what the author describes above. Of course we know this is not the same as what is used for the CAFE standards…

    Driving Schedule Test Schedule
    City Highway High Speed AC Cold Temp
    Trip Type: Low speeds in stop-and-go urban traffic
    Free-flow traffic at highway speeds
    Higher speeds; harder acceleration & braking
    AC use under hot ambient conditions
    City test w/ colder outside temperature
    Top Speed 56 mph 60 mph 80 mph 54.8 mph 56 mph
    Average Speed 21.2 mph 48.3 mph 48.4 mph 21.2 mph 21.2 mph
    Max. Acceleration 3.3 mph/sec 3.2 mph/sec 8.46 mph/sec 5.1 mph/sec 3.3 mph/sec
    Simulated Distance 11 mi. 10.3 mi. 8 mi. 3.6 mi. 11 mi.
    Time 31.2 min. 12.75 min. 9.9 min. 9.9 min. 31.2 min.

    Stops 23 (city)

    None(highway) 4(high speed) 5(AC) 23(cold(city))
    Idling time 18% of time (city) None (highway) 7% of time (high speed) 19% of time (AC) 18% of time (cold(city))
    Engine Startup* Cold Warm Warm Warm Cold
    Lab temperature 68–86ºF 95ºF 20ºF
    Vehicle air conditioning Off Off Off On Off

  • BBerman

    @Shines @Jeff – Thanks for the corrections. Despite speaking with a couple of experts before posting, we got some of the story wrong. See correction/update. Yet, at the end of the day, these first idle-stop vehicles still show no improvement (at least on the label), which is a definite shortcoming.
    Brad Berman, Editor

  • Yegor

    I did a test today:
    From the garage I drove 1 minute 15 sec and hit a traffic light.
    My car computer fuel economy was 13 L / 100 km.
    I waited 40 seconds on the traffic light and my car computer fuel economy went to 16 L / 100 km! a drop of 23%!
    On each next traffic light I was loosing a few % on fuel economy. I guess my idling at traffic light was about 25%.

    Chevy Malibu 2008 had 22 MPG city and 32 MPG hwy
    Chevy Malibu 2008 Hybrid had 24 MPG city and 32 MPG hwy

    I think that 10% city fuel economy improvement is a good estimate of Idle-Stop Systems.

  • live cars

    This is reductions! The test has to be changed!

    thanks posy

  • Yegor

    I did another test yesterday.
    I live in a suburb. I drove 17 kms (10.5 miles) to my destination in 25 minutes on off peak hour with no traffic (my average driving speed was 45 mph).
    It means that I was suck on traffic lights (idle) for 45% of the time!!!
    I know for sure that in downtowns usually it is much worse! Downtown Idling: 80% of the time on the road?

    The test has to be changed!