Highway fuel economy is for suckers
Is highway fuel economy even relevant anymore?So, the Ford Focus is a better deal than the Toyota Prius, and GM offers more vehicles that achieve 30 mpg or more than any other automaker. Of course, ONLY (and maybe not even then) based upon perfect world highway fuel economy.
So, what percentage of your commute is a cruise-controlled 55 - 65 mpg on a flat surface without any wind resistance?
Most people, even in small towns, stop at a few stop signs or red lights, conditions that reduce fuel economy significantly. Suddenly, 30 mpg is more like 20-25 mpg, or even worse, depending on how many stop lights you actually hit. Then there is the kind of congestion that you find in large cities like LA and Chicago. In such conditions, the Toyota Prius has been demonstrated to average almost 60 mpg. In tough urban congestion the Focus might not even achieve 20 mpg.
Yet, according to transportation studies, congestion is increasing and it's going to increase significantly in the future. So, is highway fuel economy even relevant anymore? Even worse, isn't marketing highway fuel economy deceptive?
Labels: fuel economy, Hybrid Vehicles, toyota prius
posted by Dahcredyns at
7:40 AM
20 Comments:
Even more evidence that the automakers like Ford and GM don't care at all about the consumer.
And even more reason why these companies should be eliminated.
My friend in CA (San-Jose) says, his Prius averages 44mpg and he drives mostly freeways, though not much. So, you claim of 60mpg is generally unproven. 45-50, more for hypermilers... not 60. Though, I agree that 30mpg on the highway tend to average to 25 in mildly congested area, and can drop below 20 in the congested city.
LB-
Cars.com did a several day test of a number of diesel and hybrid vehicles in urban traffic. They averaged about 56 mpg with the Prius and achieved more than 60 mpg on some days.
That's fuel economy that I've reproduced in a Prius many, many times, as have many others.
I know you drive a Camry hybrid, but what's your beef with the Prius anyway?
The 60mpg Dahcredyns mentioned is in congestion..
I can vouch for that. My commute is on the infamous Long Island Expressway (Interstate 495) here in New York, known as the world's biggest parking lot. :-D
Crawling along, my '07 Prius would be spending most of its time in electric-only mode, and I can get 60mpg crawling along at 15mph in heavy congestion. The heavy congestion basically FORCES you to hypermile, LOL.
Then I got my New York State Clean Pass tags for my Prius and now I zip down the HOV lane at 60mph. I still get 48mpg doing that though.
To even things out, they could give the "city" and "highway" fuel economy and then give a "combined" which is the average of the two.
To answer the author's question, I think that highway fuel economy is important... for some. But, it is up to the consumers to be informed and to not only look at the "highway" value, especially if they know that they will be spending a lot of time on congested roads.
To lb: Just in case you were not aware, the Prius drivetrain is made so that when you are in stop-and-go traffic, you are running on batteries ("infinity" mpg - no fuel). When you are cruising at a constant speed on the highway (which is when internal combustion engines are the most efficient), you are running on gas. So, it is possible to get HIGHER mpg (like 60 mpg) in traffic than on the highway - without using "hypermiler" tricks.
I like this cars..
It looks cool
The article is correct. The real story with automobile endurance, durability, economy etc. relates solely to the vehicles' everyday jobs, not to anything they occasionally do that just happens to be part of their job description. The culprits are the usual suspects: The fawning American public, automakers, big oil(Birdshot Cheney's friends), Congress (you voted for 'em, live with it!) and the Wall Street adventure artists of tomfoolery to which the rest of the participants dance.
Carmakers must now be held to very high, strict and enforceable standards or they will just find a new Suburban assUalt Vehicle to unload on the gullible (I include myself), o'erweaning and unconsciously duplicitous public, another CAFE wolf in sheep's clothing--to mix a metaphor--and to continue the same shell game for as long as the mighty few can further enrich themselves while pretending to be helping the rest of us. Dick Cheney is not the enemy--he is a mere figurehead for the enemy; ourselves.
I can vouch for that. My commute is on the infamous Long Island Expressway (Interstate 495) here in New York, known as the world's biggest parking lot. :-D
Forget to turn on AC?
Crawling along, my '07 Prius would be spending most of its time in electric-only mode,
Yep, and electricity is obtained from burning gasoline. In that, the efficiency of the mechanical transmission is higher than a combination of generator + electric engine.
60 mph is not efficient, because of the air resistance, yet the difference should not be 48mpg vs 60 mpg. It is way TOO big.
BTW, it is a well known fact that many people allured by these 50-60 mpg claims are buying hybrids and getting far less. Guys, why not adding a little bit of honesty? 40-50 mpg is great by itself, comparing to 15-20 of other cars in a congested place.
LB-
Nobody is saying that we only achieve 60 mpg or more in a Prius, just that in slow congestion, such as what I used to drive regularly in NorthEast Los Angeles, I could often average around 60 mpg from my home to downtown LA and back, a round trip of less than 20 miles.
Yes, the average speed during this commute is probably less than 25 mph - if even that - but these are every day conditions for tens of thousands of people driving into downtown LA, as well as many other major cities. These horrible conditions bring out the best fuel economy in many hybrids AND they bring out the worst fuel economy in most other vehicles.
Yes, there are days when the same commute only achieves 50 mpg. But, again, there are still many days when the average is closer to 60 - days with low speeds, lots of coasting and braking.
And that's why many automakers love to talk about only highway fuel economy. Because for most conventional automobiles, achieving just 25 mpg is considered excellent city fuel economy. Most conventional vehicles don't even achieve 20 mpg in the city - conditions that on some days, I can achieve 60 mpg.
And according to transportation studies, this type of congestion is only going to become more common, while increasing in severity.
50 or 60 versus 20.
If the future is congestion, then hybrid technology becomes that much more important, unless the problems of oil dependency are suddenly going to disappear. And, while some will ask about hybrid costs, economies of scale will bring down hybrid costs, and isn't 50 or 60 versus 20 worth the investment?
LB:
Yes, 60mpg with the AC on. No way will I ever put down the windows during a summer heatwave while crawling along in heavy traffic on the LIE.
The electricity in the battery is obtained from the gasoline engine, but keep in mind that electricity is obtained from the gasoline engine when it is running at its most efficient RPMs (such when the car is cruising along at 40-60mph). That's the reason why the Prius uses a differential gearset transmission-- The gasoline engine, when needed, runs in a narrower range of RPMs than in a normal car.
The engine also runs in an Atkinson cycle, not the less-efficient Otto cycle in regular car engines.
Also, the electricity is also obtained from regenerative braking-- Kinetic energy that normal cars waste by friction braking.
Lots of Prius owners beat the EPA numbers easily and they do their best to spread the know-how among other Prius owners here: http://www.priuschat.com
I don't particularly care about getting 60mpg, because when I do I'm crawling along in a friggin' traffic jam. I hate traffic jams. But at least I don't have to waste stupid amounts of gasoline while sitting in one.
Don't take my word for it. If you know anyone who lives on Long Island and owns a Prius, ask him or her to take you on a ride down the LIE around the Van Wyck interchange during rush hour, and stay out of the fast HOV lanes. Watch the MPG readout. :-P
Yes, 60mpg with the AC on
That is definitely a fact, none would believe! The slower you drive, the more AC affects the fuel efficiency. E.g. in Camry the MPG often drops from 40 to 30! How Prius is different from Camry to make such a difference? It only 25% lighter! The same dual-mode hybrid from Toyota.
And what is much more important, these 60 mpgs do not project well onto an average driver. This the proven fact. There was even a scandal 3-4 years ago with a lot of hybrid car drivers who claim they average only 40+ mpg.
PS: It is also a huuuuuge question, how, you are measuring this 60 mpg. Is it 60 mpg average for say a year? If it is not, then this is not serious.
PPS: On the highway, at constant speed of 40-55 mpg, the engine is also working in an optimal mode. In addition, there is virtually no breaking and nothing needs to be regenerated. When you are regenerating, you lose A LOT!!!
"PS: It is also a huuuuuge question, how, you are measuring this 60 mpg. Is it 60 mpg average for say a year? If it is not, then this is not serious."
How can it not be serious?
These are the conditions that produce the worst fuel economy and the worst emissions from most automobiles, except full hybrids. To say that fuel economy in these conditions doesn't matter is very poor thing to say.
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This post has been removed by the author.
I did not say, that it did not matter, I said that the measurements were likely to be incorrect and show only peak fuel efficiency only, instead of the average. A modern hybrid is a very convenient car to show super-figures. Take the charged battery before entering a congested street, almost discharged battery after the congested street and get these enormous fuel efficiency figures. Geee, this car goes most electric!!!! Yeh, yeh, yeh, and it burns a ton of fuel later.
In addition, I would never believe that it gets 60 mpg with AC on.
This is the simple energy calculation. In an automobile the A/C system will use around 5 hp (4 kW) of the engine's power. Quote from the Wikipedia. Let your Toyota AC be super efficient and use only 1 Kw.
Gasoline contains about 34.8 MJ/l or 132 MJ/US gallon. This is about 9.67 kWh/l or 36.6 kWh/US gallon.
Gasoline engine efficiency (plus what you lose on the generator) is less than 25%. That means, that one gallon of gasoline produces about 9 KWh of energy. Even with the Atkinson cycle! Diesel gets 50% more, but this is a different story, you know.
Let us proceed to the real-world, though somewhat pessimistic, example. Say, you are driving 5 miles in an hour. Since you AC requires 1 Kw of power, your AC consumes 1 KWh or more than 0.1 of the gallon in a gasoline equivalent. Assuming that you drive one hour. In that, you car crawls the distance of only 5 miles. This is an equivalent of about 50 mpg, based on AC usage ONLY!!!
Now, you are talking about 60 mpg driving and ACing combined!!! In this case that will be around 30 mpg. If you drive a less congested route, it will be somewhat more, generally between 40 and 50mpg, which corresponds to the observations of my own. And of my friends :-)
PS: I know you drive a Camry hybrid, but what's your beef with the Prius anyway?
My beef is that these tests don't really include AC and/or congested roads. BTW, as I told you Camry and Prius should have similar figures. The curb weight difference is about 25%. So, I should expect 40 mpg with heavily using AC? This is not what I get.
Pardon, correction, one tenth of a gallon of a very economic usage is equivalent of 5 mpg at the very optimistic assumption that Toyota's AC is 4 times more efficient than that of the average car. So, you won't get 30 mpg. However, you will easily loose 5-10 mpg, which is a lot and won't achieve this mythical figure of 60mpg.
And finally, you can also see the data of the independent tester, which is not interested in selling any vehicles! Toyota Prius averages 48 mpg
Uuups, a correction again. The original estimate of 25-30 mpg was correct. AC takes about 1kwh (or more), this the real figure. Hence, in the above example 1kwh goes to the wheels to drive 5 miles and 1 kwh goes to the AC. So ~ 25 mpg is the real fuel economy in case of hot weather and a congested city, not 60 mpg.
It looks like 60 mpg, perhaps even more, could be achieved in some ideal conditions by the good and thrifty driver who does not accelerate much and rarely turns AC on, but this is the totally unrealistic assumption for the average driver and hot weather. The average driver will get what the EPA and Google obtained 45-55 mpg. Or even less, if she likes to drive agressively.
Are you even aware that the Prius (since '04 model) uses a All-electric Air Conditioning system? I have sat in my Prius set at 72 degrees in 100 degree heat for 15+ minutes without the engine turning on. So typical A/C calculations don't apply here. And I have gotten 50-60 mpg on certain driving segments with windows closed-A/C on very hot days as well.
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