Toyota Prius hybrid left side

Why your car doesn’t match the EPA ratings

Autore: ExtremeTech

Toyota Prius hybrid left side

The window sticker says 25 mpg average fuel economy and you’ve never seen better than 22 mpg. What gives? The reasons range from changing technology and how to measure it, to automaker miscues, to journalistic rounding converting the world’s fuel economy nomenclature, to our own driving habits. When it comes to fuel economy, “we’re all victims” translates here to “we’re all culprits.” Here are reasons why the mileage on the Monroney (window) sticker doesn’t match what you get.

EPA can’t keep up with fuel-saving technology testing

Stop us if you’ve heard this one before. Innovative engineers develop new technologies faster than the government can revise its test methods. Start-stop technology, which shuts off at a traffic light and refires when the driver’s foot lifts off the brake, saves 1-2 mpg in city mode testing but the EPA’s tests have in the past just used brief stops, not the 30-60-second traffic lights that urban drivers encounter. For years, automakers omitted start-stop because it added $ 100-$ 200 in costs for a beefier battery and starter motor. Now cars are coming to the US with start-stop that may improve economy beyond what the EPA tests estimate.

On highway testing, the EPA may assume more energy-conscious driving than really exists: top speed of 60 mph, average speed of 48 mph, no air conditioning, and slow acceleration. Cars with better aerodynamics may do better at the higher speeds we drive, so there’ll be a car-to-car variance from true mpg.

EPA testing for fuel efficiency doesn’t reflect the way we actually drive, especially on the highway. The government’s highway test involves a top speed of 60 mph, an average speed of 48.3 mph, no use of heaters or air conditioners and an achingly slow initial acceleration in which it takes more than a minute to go from zero to 50 mph. Blame some of it on the government’s aging lab equipment, such as stationary rollers, being unable until recently to replicate true highway speeds.

Automaker testing errors

Automakers make mistakes in their testing, too. Hyundai for two years crowed that every one of its two most popular models, Sonata and Elantra, got 40 mpg in highway driving, unlike competitors. Late this year Hyundai admitted it made mistakes in dynamometer coast down testing (it simulates real world resistance) affecting 1.1 million 2011-2013 Hyundais and Kias. The Sonata and Elantra were downgraded to 39 mpg highway.

BMW restated the mileage of its 2012 BMW 328i automatic from 36 mpg highway to 33 mpg, and from 24 mpg city to 23 mpg. Automaker mistakes on testing are rare. The previous mpg restatement was in 2001. The Hyundai mpg restatement was big because so much of Hyundai’s advertising was built around hitting 40 mpg rather than price or features.

Mistaking highway for overall mpg

Automakers typically advertise one mileage number, almost always the best one. Heck, always the best one. The EPA ratings include estimated mpg in city driving, highway driving, and a combined number that is 55% city driving. Each combination of engine and transmission is rated separately. The best-selling Honda Accord gets 36 mpg in highway driving with a four-cylinder engine and continuously variable transmission, or 30 mpg combined. But variants of the Accord get as little as 22 mpg combined.

In the past, manual transmission cars got better mileage. Now that’s not always the case. The Ford Focus, one of our 10 Best Tech Cars, is rated 23 mpg city, 32 mpg highway, 26 mpg combined with a manual transmission. With an automatic, it’s 27 mpg city, 36 mpg highway, 31 mpg combined. When you compare cars on fuel economy, make sure it’s an apples to apples comparison. If you see mileage like this, 27-36-31, it’s in this order: city, highway, combined.

User error: We’re not fuel-efficient drivers

Little things we do every day mess up fuel economy: braking late for a traffic light we see far ahead, accelerating quickly to get ahead of the jerk in the next lane, and not checking tire inflation. According to the EPA, for every 3 psi of underinflation, you lose 1% fuel economy, and a lot of cars run with tires underinflated by 10 psi. A serious engine problem such as a bad oxygen sensor can cut fuel economy by as much as 40%. But, says the EPA, a clogged air filter doesn’t affect fuel economy with today’s cars but it does reduce performance. If your car has an Eco setting, you may get gentler acceleration or weaker air conditioning when it’s enabled, but it does improve economy.

Milers per gallon doesn’t work as well as liters per 100 kilometers

Which is better: Upgrading your 15 mpg SUV to a new model that gets 20 mpg, or swapping your 33 mpg subcompact for one that gets 43 mpg? The percentage improvement is greater with the new SUV, 33% vs. 30%. Americans track economy as miles driven per gallon of fuel consumed. Most of the rest of world measures economy as units of fuel consumed for a fixed amount of driving, typically liters per 100 kilometers. It has the advantage of being linear and more easily comparable especially at the extremes (gas guzzlers and hybrids). If a new hybrid jumps from 40 mpg to 43 mpg, Americans may think, “Wow! An extra 3 mpg”), while the rest of the world sees the improvement (lower is better) from 5.9 to 5.5 liters per 100 km — nice but not a reason to dump the old car.

VW XL Qatar

The 20% error: Was that US mpg or imperial mpg?

Read a story online and you have to ask if the writer hails from the UK or Ireland, sometimes Canada, where imperial gallons are cited. They’re roughly 1.2 US gallons. Add in rounding errors if the writer saw a liters-per-100-kilometers rating and converted to the nearest round number, and the amount could be off by 25%. Consider the recent story on Audi and VW working on the 300 mpg car. It’s the L1 concept, meaning a highly efficient car that uses just 1 liter of fuel per 100 kilometers. That translates to 282 imperial mpg, which could be rounded to 300 mpg with only a little bit of fudging. So it’s a 300 mpg car if you use imperial measures and allowing for rounding, a 250 mpg car if you convert to US mpg (based on rounding), or 235 mpg if you directly convert liters per 100 kilometers to US mpg. 235 mpg sounds fantastic, but 300 mpg sounds even more fantastic.

Now read: The 10 best tech cars of 2012

6 thoughts on “Why your car doesn’t match the EPA ratings

  1. avete dei riassunti brevi di inglese su ” industrial revolution”,” the french revolution” e “napoleonic wars” grz in antip mi va bn anke se avete una di queste grz mille vi daro molti punti
    a ilenia ancora a parla stai!? ma perke nn kiudi un po quel cessò??? io mi riferivo alle troiè come te(ilenia) e nn a tutte.ma perke nn prendi na bell zukkina e te la fikki dentro a sangue prorpio!? ke sl quello sai fare ne troiòna porcona. ke ce nn ti vergognare lo so ke lo vuoi(il cazzò mio) dammi l’indirizzo ke ti vegn a fottere un po…..

  2. Magari evitata di fare copia e incolla dal traduttore che sono capace pure io.

    PEATLANDS: WASTELAND OR HERITAGE?

    Peatlands have played a very important role in shaping the history, culture and economy of Ireland. This is not surprising because whit 17% of the land surface covered in peat Ireland has proportionally more than any other country in the world, except for Canada and Finland. These peatlands have long been regarded as wasteland fit on only for rough grazing or for cheap, but hard-won, fuel. In fact they are one of our great natural assets not only as an energy source, but as some of our last wild areas, described by David Bellamy as one of the wonders of the world.

    Caution: Bogs and fens can be dangerous places with deep pools, quaking surfaces and sometimes deep cracks on the margins. It is strongly advisable not to venture out alone.

    PEATLANDS THROUGH THE AGES

    A glance at Irish history will give an idea of the importance of our peatlands down through the ages. In north mayo we find that Stone Age and Bronze Age farming communities were gradually overwhelmed by the rising tide of peat as spread down from the hills and up prom wet depressions, eventually merging. In the process the ancient field boundaries and cultivation ridges were buried and preserved. All this happened thousand of year ago and removal of the turf exposes the settlement today.

    Increasingly from that time, bogs presented formidable obstacles to communication and ancient route-ways often followed the drier lands between them, as they still to today. Where such “corridors” were narrow they became known as “passes” (e.g. Tyrrellspass Co. Westmeath), as thought referring to mountains! Where there was no choice but to cross tracks were made from timber and these are occasionally revealed by turf cutting. Again they have given us place names, the Irish name for such constructions being Togher.

    Tradition has it that in the 16th century the Irish army, under O’neill, marched south to Kinsale by crossing the frozen bogs during an exceptionally cold period, getting to West Cork in record time. An adequate road system traversing our major peatlands is a modern creation – much of it put in by the British authorities after the 1798 rebellion – for example, the “Military Road” through the Wicklow Mountains is one of a number of such in that country. The Ballina to Belmullet road in Co. Mayo is very recent, dating form the pre-famine period (1830s). Prior to that access was very difficult over a vast area of West Mayo and was mainly by sea.

    GOING TO THE BOG

    The Irish word for peat -“moin”, “mòna”- is commonly found in place names e.g. Ballynamòna, and of course in associated particularly with Bord na Mòna, the Turf Development Board. The word “bog”, in common use in the English language, in derived from the Gaelic word “bogach” meaning soft.

    “Going to be bog” (to cut turf) is a commonly used expression in “boggy” parts of the country. “Turf”, related to “torb” in German, and “turb” in French, refers to a piece of peat cut for fuel. Only in England does it refer to horse racing! Turbary – of French derivation – refers to land where turf may be dug for fuel.

    WHAT IS PEAT?

    Peat consist of 95& water, the remainder being made up of partly rotted plants plus small quantities of animal remains, pollen and dust. In ordinary farm or garden soil dead plants and animals decay within a few years, returning their nutrients to the soil. In certain conditions however, for examples where the land is waterlogged, the micro-organism (bacteria, fungi and small invertebrates) which cause decay are unable to survive so that the dead matter gradually accumulates to form peats, of turf.

    Peat began to form in Ireland over 8,000 years ago, i.e. about 2,000 years after the end of the last Ice Age. Since then deposits have built up to more than 10m in depth in places. As the peat accumulates, dust and pollen falling onto the surface become trapped and preserved. When a piece of turf is examined it is possible to say not only from which plants it is formed but also, by examining and identifying the pollen, the sort of woodland or agricultural land that surrounded the bog down through the ages. It is even possible to detect the beginning of the industrial revolution from particles of iron in the peat and such event as the Chernobyl nuclear accident in 1986 will also have been recorded by the bogs. It is therefore possible to build up a picture of the history of the country or region from an examination of the bog.
    Grazie, se non avete intenzione di farlo semplicemente non criticate. A me sta roba me la danno da fare quasi sempre a scuola dall’inizio dell’anno avrò tradotto chissà quanto, e non mi pagano proprio un tubo. Non mi padre di aver obbligato nessuno, ho chiesto semplicemente un favore visto che ho poco tempo, poi sta a voi scegliere se farmelo o no.
    Ripeto. Non vi obbliga nessuno. Non volete farlo? OK. Chiuso il discorzo.

  3. Aiutatemi a tradurre questo testo.
    Questa è l’ultima parte ma ce ne sono 4, quindi 40 punti.

    Ecco il testo:

    Deforestation is especialy present in the tropical areas because of the poor economic conditions of the countries were big rainforests are located. The leaders of those countries sell the rights to logging companies, which use large machines such as bulldozers to cut down trees which supply firewood and wood for the building industry.
    In addition to trees being destroyed, hundreds of animal or plant species are destroyed along with them. The tropical rainforests are in fact home of half of the Earth’s living beings. Besides, the destruction of forests will also have serious effects on the global climate, on agricolture and water supply. Water scarcity will cause food scarcity, and all this will lead to high food prices, thus causing economic and political instability, especially in the developing countries. Today, people are beginning to realize that, in the near future, the degradation of the environment will challenge our economic system and that, in order to have a sustainable development, we will have to replace our fossil-fuel-based system with a global renewable-energy-based economy.
    parte 1:http://it.answers.yahoo.com/question/index;_ylt=AoftCW2f3HHDEvbI6DRSzDrwDQx.;_ylv=3?qid=20090315060244AAeNikQ
    parte 2:http://it.answers.yahoo.com/question/index;_ylt=As44c_mpLrSMnTpErSaI_9LwDQx.;_ylv=3?qid=20090315060901AAQ5KRC
    parte 3:http://it.answers.yahoo.com/question/index;_ylt=AhVO96Cud380XnxvvP882o7wDQx.;_ylv=3?qid=20090315060910AABN8lD

  4. Chi sarebbe cosi gentile da farmi un testo in inglese dove parla degli stati uniti d’america, quindi le caratteristiche fisiche, Obama, l’Indipendence Day ecc…. Grazie mileee <3

  5. Vorrei il riassunto di queste 3 parti (in inglese)

    parte 1:Human beings who had evolved from apes, became soon the dominant species on earth as they are the most intelligent and enter prising of all animals, the only beings who have always had the desire to explore and understand phenomena around them. Urged by the desire to improve his living conditions and his quality of life, man has also achieved great inventions is the field of science and technology. But man’s influence has also had an impact on the abitants and the living condition of many plants and animals. This happens because, has technology and industries become more advanced, more and more of the natural resources available are being used. Amoung these are perpetual, renewable and non-renewable resources. Unlike perpetual resources (e.g. sunlight), which are unlimited, both renewable and non-renewable resources have a limit, but renewable resources (e.g. trees) can be replaced if they are used and produced at the same time.

    parte 2:Deforestation is especialy present in the tropical areas because of the poor economic conditions of the countries were big rainforests are located. The leaders of those countries sell the rights to logging companies, which use large machines such as bulldozers to cut down trees which supply firewood and wood for the building industry.
    In addition to trees being destroyed, hundreds of animal or plant species are destroyed along with them. The tropical rainforests are in fact home of half of the Earth’s living beings. Besides, the destruction of forests will also have serious effects on the global climate, on agricolture and water supply.

    parte 3:Water scarcity will cause food scarcity, and all this will lead to high food prices, thus causing economic and political instability, especially in the developing countries. Today, people are beginning to realize that, in the near future, the degradation of the environment will challenge our economic system and that, in order to have a sustainable development, we will have to replace our fossil-fuel-based system with a global renewable-energy-based economy.
    per la PARTE 1:

    http://it.answers.yahoo.com/question/index;_ylt=Ai1FX5QNLB0dCdM8HEPbusHwDQx.;_ylv=3?qid=20090315104446AAsWxig
    voglio il riassunto in inglese!! non la traduzione…

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