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EPA's Gasoline Efficiency Tests Provide No Valid Information At All (hotair.com)
schwit1 writes from a report via Behind The Black: The tests the EPA uses to establish the fuel efficiency of cars are unreliable, and likely provide no valid information at all about the fuel efficiency of the cars tested. Robert Zimmerman reports from Behind The Black: "The law requiring cars to meet these fuel efficiency tests was written in the 1970s, and specifically sets standards based on the technology then. Worse, the EPA doesn't know exactly how its CAFE testing correlates with actual results, because it has never done a comprehensive study of real-world fuel economy. Nor does anyone else. The best available data comes from consumers who report it to the DOT (WARNING: Source may be paywalled) -- hardly a scientific sampling. Other than that, everything is fine. Companies are forced to spend billions on this regulation, the costs of which they immediately pass on to consumers, all based on fantasy and a badly-written law. Gee, I'm sure glad we never tried this with healthcare!"
"Companies are forced to spend billions on this regulation"
Well, not VW...
Linux, you magnificent bastard, I read the fucking manual!
Too subject to variation cause by the drivers. Even the weather and temperature on the day would have a huge impact. All car manufacturers would be insisting their cars were tested on the coldest, highest humidity, but no rain and no wind day.
first, we all know there's a reasnonable correlation between epa estimates and our observed results. It's quite good. Second there's been lots of tests on other standards to show they perfrom good real world estimates. The author is nit picking that a specific set of linear combinations of tests hasn't been correlated. That is if you have 5 test that are correlated with real world measurements and you average them it is true that the average has not been tested but logically we can estimate it's error from the other tests.
who writes this crap
Some drink at the fountain of knowledge. Others just gargle.
The article makes a glaring error when it says "When the EPA tests for CAFE compliance...". EPA does no such thing...EPA tests for the numbers that go on window stickers. CAFE testing is the responsibility of NHTSA, not EPA. Some may think this is nit picking, but I find it hard to take this article seriously if the author is not even aware of who does which testing.
The gas mileage numbers that the EPA requires on new car window stickers are not determined the same way as the gas mileage used for CAFE fleet efficiency regulations. The former isn't perfect, but is a lot closer to real world performance than CAFE is.
I'm disappointed that this was posted with such a ridiculous assertion in the headline. Are you kidding me? Certainly the tests aren't entirely accurate, and I've complained about them, but saying that there's "No Valid Information At All" is bogus. Obviously you can go to the fueleconomy.gov site and see that there's a correlation between big, heavy, overpowered cars using lots of fuel and smaller, lighter, lower-powered cars that sip gas. The EPA has updated their tests a couple of times, most recently around 2007 following controversies that the Toyota Prius didn't achieve real-world fuel economy as good as what was on the window sticker. They also didn't try to factor in air conditioning or other features that are now common on cars.
The original 1970s-style tests produce numbers about 30% better than the end result today (an adjustment around 1985 reduced MPG numbers by about 15%, and the second one around 2007 brought it down by another 15%). Notably, government fuel economy tests in Europe and Japan still have ridiculously optimistic figures, so U.S. figures are much, much more accurate and reasonable compared to other places around the world.
Are EPA figures perfect? No. I personally think they went a bit too far in the most recent adjustment, since my (pre-dieselgate era) 2006 VW Jetta TDI gets MPG figures almost exactly matching what it originally had on the window sticker when I bought it.
And if this is all about people expecting to get super MPG when driving at 90 mph all the time, just stop complaining. That's not an appropriate expectation for what you should get out of these tests.
Slashdot editors: how did this garbage get posted here? Why not go straight to the quoted Wired article with the hyperbolic title?
Interestingly, that article contradicts itself: "a 2013 Consumer Reports study tested more than 300 cars, and found 90 percent landed within two miles per gallon of their EPA-approved ratings."
Yeah, testing standards aren't perfect. That doesn't mean that the government is incompetent and is trying to fuck you.
To those thinking the EPA should just drive the cars, even that won't actually get very accurate results. Real-world fuel efficiency depends on so many factors that it would be impossible to reliably and accurately measure them all. For example, so-called hyper-miler enthusiast employ driving techniques to maximize their fuel efficiency. Conversely an aggressive driver could easily drop fuel economy in half. Then we have differences in temperatures, altitude, and terrain across the country.
So with that in mind, I think the current, 40-year old testing regime is probably still our best bet. It may not tell you how much fuel economy *you* will get, but since it's done under very controlled and consistent circumstances, it can give an indication to you how it will do relative to other cars. Honestly that's the best we should expect.
I fear we're going to meet the same problem with "real-world" emissions testing. I don't know of any car out there that can meet standards all the time. Take the cleanest car and get it to accelerate up a grade and it will dump pollutants. Or punch it off the light and you'll dump a lot more NOx and particulates than if you accelerate at a more reasonable rate.
In short, "real-world testing" is fairly meaningless. The only way to actually accomplish this is to have sensors and recorders on every car all the time and measure it and average it over time (and after the fact).
The EPA tests were originally developed to quantify pollution generated by cars in the L.A. area, and using those tests to quantify gas mileage came later.
The EPA city cycle was not meant to represent the stop-and-go driving in Manhattan during rush hour. Rather, it was intended to be typical of an automobile trip in the L.A. area conducted on "surface streets", meaning major arterial roads that have stop lights and are not freeways. The average speed of that cycle is about 20 MPH. The EPA highway cycle was not meant to represent bombing down an open Interstate at 10-over a 70 MPH speed limit. Instead, it was to represent a trip on the 405 freeway in Los Angeles in the days before that road became a parking lot -- the test was meant to represent "moderate traffic" levels where the average speed is about 50 MPH.
Not only may your miles-per-gallon vary, the amount of BTUs in a gallon of gas can also vary downward from an alcohol-free summer blend that was probably the standard for the test -- the test conducted on rollers somewhere in Ann Arbor, MI doesn't actually measure the quantity of fuel used but instead measures the combustion products out the tailpipe and performs a mass balance with that standardized gasoline.
Taking the lower BTU fuel you may be getting into account, if you start the car engine from cold on a 70 deg-F day, don't run the A/C, and drive for about 10 miles in traffic where you average 20 MPH, you will roughly reproduce a city test, and I have found that the reading on a Scan Gauge, calibrated to tank fills, will get within 5 percent of the raw city numbers available here https://www3.epa.gov/otaq/tcld.... These numbers are considerable higher than the window sticker MPG rating available here https://www.fueleconomy.gov/. Driving on a not-that-hilly road (do this in both directions and take a harmonic average to compensate for net elevation change) on a 70-deg calm-wind day with the A/C off at a constant 55 MPH, if you can do that with angering other drivers, is a good proxy for the EPA highway test and will also get you within 5 percent.
"But no one drives that way!" someone will shout at you, and this may be true, but if you want to reproduce the EPA test conditions to see if you can match the (raw) EPA numbers, this is the way to check that.
The sticker MPG at fueleconomy.gov has had more than one "adjustment" performed to down rate it from the raw MPG. This was done because the published EPA ratings made people who considered themselves to be "good drivers" feel bad about themselves and their expensive new car purchases, and we cannot have any of that. Or rather, the "consumer" gas mileage numbers were proportionately reduced to "better reflect how real-world driving conditions on more congested city streets and with higher speed limits on highways affect mileage" whereas the Federal Test Procedure and the raw numbers for computing CAFE (corporate average fuel economy) were left the same so as to not keep changing the rules to which the car companies had to comply.
Now the down-adjusting is based on fleet averages, and your car may vary. A case in point is that Consumer Reports praised the Ford C-Max hybrid as being a lot more "fun to drive" than the Toyota Prius but slammed it for being much further off the EPA sticker in real-world driving than the Prius. Well, duh, Consumer Reports! Were you to drive both vehicles in a true "EPA city granny cycle", they probably would get proportionately higher than the window sticker as is the raw "test car" number. But left to the lead foot of a "normal driver", the C-Max with its bigger gas engine will indeed accelerate better yet use more gas than the small-engine sluggish Prius.
I also expect "eco-cars" like the Prius to suffer more from "normal driver" in relation to EPA test cycle driving because their power plants are more matched to the "granny cycle." A real "muscle car" may suffer le
Indeed, this is a pointless rant. The US uses a number of driving cycles for different purposes - FTP-75, HWFET, US06, and SC03. In terms of determining ratings that are presented to computers, US standards are by far the most stringest in the world. European cars are rated by the much less stringent NEDC, and Japanese cars by the laughable 10-15 cycle, where the highest speed involved in the whole cycle is 70 kph (under 45 mph), with an average speed 1/3rd of that.
The US cycles are regularly updated - the most recent update to the FTP-75 was in 2008. And yes, it's made them more stringent, based on... wait for it.... research on how people drive, the thing that this rant claims doesn't occur. Now, it's true that, for consistency purposes, CAFE ratings (which the buyer never sees) still use the same measure that they did back in the 70s, and that there's different measures for different types of vehicles and the like. But that's because you don't want to break your comparisons to older vehicles; anyone actually working with CAFE numbers is going to be aware of their limitations. John Smith from Podunk Arkansas isn't going to be messing around with CAFE figures; CAFE exists basically for accounting purposes, to see if the fleet is overall getting more or less efficient.
Hourglass says she knows a kid in Iowa who grows up to be president.