While messing with the numbers lets up'em

[stubeeef]

Link

Well-known motorists club AAA says many cars and trucks it road-tests fall far short of their government fuel-economy ratings.

Using that disappointing fuel economy data from hundreds of road tests in what AAA calls real-world driving, the organization plans to endorse legislation to be introduced Thursday that would require the U.S. Environmental Protection Agency (news - web sites) to overhaul its gas-mileage tests.

Environmental groups have argued for years that mileage labels are bogus, but it is significant that AAA is throwing its influence behind the bill to change them. (Related: Drivers irked as mileage fails to add up)

"There's no doubt that it helps. And it highlights the fact that it's just common sense - providing consumers with accurate information," says David Friedman, a research director for the Union of Concerned Scientists. UCS strongly backs legislation to require realistic mileage ratings.

AAA data come from tests done by drivers across the country "getting groceries, getting stuck in traffic jams, driving the same way you would," says AAA spokesman Mantill Williams.

The organization concedes that its tests aren't scientific but insists the results are representative.

Among vehicles that were farthest off of EPA: 2004 BMW Z4 sports car, which AAA says hit just 14.5 miles per gallon in combined city-highway use, vs. 24 mpg EPA rating; Chevrolet TrailBlazer SUV, 13.6 mpg in AAA testing vs. 17 mpg EPA rating; Chrysler PT Cruiser, 17.5 mpg from AAA vs. 25 mpg EPA rating.

The so-called Fuel-efficiency Truth-in-Advertising act would require EPA tests to "reflect modern driving patterns and experiences, specifically speed and highway-vs.-urban driving," says Rep. Nancy Johnson (news, bio, voting record), R-Conn., co-sponsor of the bill with Rush Holt, D-N.J. "Those are no-brainers," she says.

This is news, but probably a bit political. Here are both R and D working to change it, the upside here? Is that manufactures will actually have to build more effecient cars and trucks, they have been scamming to make their CAFE numbers. This is a benefit for everyone! But while they are going to require a more accurate test, why not put in an increase for CAFE requirments.

[miloblithe]

I seem to remember some vehicles actually doing better than their EPA ratings as well, but I can't think of where I might have read that. It does seem unlikely looking at that article, in which all the cars mentioned are drastically underperforming.

This does sound like a good effort, although any serious downgrading of most cars fuel economy estimates by the government would likely be accompanied by a drop rather than a raise in CAFE standards. Another fair point is that fuel economy depends greatly on the way people drive. You could probably get 24MPG in a BMW Z4, but very few people would be willing to drive that way, especially the kind of people who would buy a BMW Z4. Still, it would make sense to have the estimates reflect "average" driving rather than ideal driving (with respect to fuel economy).

[wordmunger]

My volkswagen passat regularly gets 29 MPG in suburban driving (some traffic, some highway). I believe it was rated at 24 city/ 31 highway. I do get about 31 on long highway drives. Even in bad traffic, it never gets as low as 24.

[MongoTheGeek]

One of the best demonstrations I can think of between measured and real numbers was on MythBusters. They bring good scientific methodologies along with the penchance for destruction.

Once they attacked the myth of AC versus windows down on MPG. The first test they hooked up a meter that read the oxygen sensor in the car which is how the EPA measures mileage. Essentially it measured the airflow into the engine and then based on stochiometric principles deduced fuel consumption. AC won by a good sized margin

The second test they ran 2 identical cars with a fixed amount of fuel until they ran out. Windows down won by a good sized margin.

[stubeeef]

Originally Posted by MongoTheGeek

One of the best demonstrations I can think of between measured and real numbers was on MythBusters. They bring good scientific methodologies along with the penchance for destruction.

Once they attacked the myth of AC versus windows down on MPG. The first test they hooked up a meter that read the oxygen sensor in the car which is how the EPA measures mileage. Essentially it measured the airflow into the engine and then based on stochiometric principles deduced fuel consumption. AC won by a good sized margin

The second test they ran 2 identical cars with a fixed amount of fuel until they ran out. Windows down won by a good sized margin.

Very interesting!

[ziwi]

One can only hope that this will make the auto makers change, but I for one will not hold my breath. The mileage that we get now is not much different from 20 years ago - that is really sad. What is more sad is that we are still dependant on the fossil fuels. This may make a change and that is good, but does it just make us rely on these types of fuels longer than we should?

[miloblithe]

Originally Posted by MongoTheGeek

One of the best demonstrations I can think of between measured and real numbers was on MythBusters. They bring good scientific methodologies along with the penchance for destruction.

Once they attacked the myth of AC versus windows down on MPG. The first test they hooked up a meter that read the oxygen sensor in the car which is how the EPA measures mileage. Essentially it measured the airflow into the engine and then based on stochiometric principles deduced fuel consumption. AC won by a good sized margin

The second test they ran 2 identical cars with a fixed amount of fuel until they ran out. Windows down won by a good sized margin.

What sort of speeds where they running these tests for? Obviously, the higher the speed, the worse the windows-down strategy will be.

[craigdawg]

I predict the auto industry will:

1. Spend a boad load of cash to lobby Congress against this act
2. Employ some scare tactics about how much more automobiles will cost and how many jobs will be lost as a result of this act
3. Change the subject and talk about how they're developing hybrids and fuel cell vehicles, etc.
4. Ultimately maintain the status quo

I hope I'm wrong.

[Dont Hurt Me]

Originally Posted by craigdawg

I predict the auto industry will:

1. Spend a boad load of cash to lobby Congress against this act
2. Employ some scare tactics about how much more automobiles will cost and how many jobs will be lost as a result of this act
3. Change the subject and talk about how they're developing hybrids and fuel cell vehicles, etc.
4. Ultimately maintain the status quo

I hope I'm wrong.

This sickens me and i think you will be right. As foreign automakers work on fuel economy the big three are doing the same garbage from the 70s....Big V-8s and 4 x 4s and then spinning the numbers. We should demand 30 mpg from vehicles and those that cant should pay the gas guzzler tax. There just isnt a reason for everyone driving 250 hp cars and trucks. Problem is Congress works for them not us. Its ashame that we now have bigger gas hogs then we did in the 70s and Congress encouraged this or rather the automakers encouraged Congress through lobbiest and donations. Congress is in the big threes pocket.

[MongoTheGeek]

Originally Posted by miloblithe

What sort of speeds where they running these tests for? Obviously, the higher the speed, the worse the windows-down strategy will be.

45 mph iirc.

Dynamic resistance goes up with the square of the velocity so yes, windows down would get progressively worse, but the difference in drag coefficient may not be constant and I can actually envision some scenarios where the windows down might actually lower drag coefficient by tripping the flow from laminar to turbulent.

[mactastic]

Originally Posted by miloblithe

What sort of speeds where they running these tests for? Obviously, the higher the speed, the worse the windows-down strategy will be.

I saw that one too, and I didn't think it was fair of them to make the claim without testing at various speeds. Think 5MPH. AC is a clear loser there. Windows open would create so little drag as to be negligible. 150MPH? Waaaay different story. Also most people don't drive with all 4 windows down, how would only 1 or 2 windows down perform?

I did feel sorry for the guy who had to run with the AC on full blast for that many hours.... Brrrrrr.

[Lacero]

I read about advances in automotive technology such as the use of ceramic engines that could mean better gas mileage and near lifetime performance without the need for an oil change. However, the car manufacturers want to keep that technology off the market because it would mean their business could not sustain profitability for their investors. Car manufacturers and oil industries have a lot at stake in keeping low MPG on cars built today.

[MongoTheGeek]

Originally Posted by mactastic

I saw that one too, and I didn't think it was fair of them to make the claim without testing at various speeds. Think 5MPH. AC is a clear loser there. Windows open would create so little drag as to be negligible. 150MPH? Waaaay different story. Also most people don't drive with all 4 windows down, how would only 1 or 2 windows down perform?

I did feel sorry for the guy who had to run with the AC on full blast for that many hours.... Brrrrrr.

Thing is that AC lost at 45.

45 is a good representative speed. Average speed in many areas during rush hour, Speed limit on many secondary streets.

There are so many variables to test that would have made for a really dull month of taping and a really dull hour of TV.

[KingSleaze]

Originally Posted by miloblithe

What sort of speeds where they running these tests for? Obviously, the higher the speed, the worse the windows-down strategy will be.

That was the problem with the results that they 'demonstrated' on Mythbusters IMO. During the first test they ran at 45 mph. During the second test, they ran at 30mph.
They need to run it on a superspeedway and at higher speeds.