Posted on 09/22/2005 4:57:12 AM PDT by grundle
http://www.wfaa.com/sharedcontent/dws/wfaa/daybreak/consumernews/stories/wfaa050920_wz_crmpg.769b7aa2.html
Consumer Reports: Overstating gas mileage
07:22 AM CDT on Tuesday, September 20, 2005
Consumer Reports
When shopping for a new car, the gas mileage is a top priority these days. Automakers' mileage predictions are based on lab tests like the ones conducted by the Environmental Protection Agency.
Cars are strapped onto a machine called a dynamometer. It turns the front wheels while a computer directs the driver to speed up and slow down.
Consumer Reports just analyzed the fuel economy data of every vehicle it has tested in the last five years. CR's Kim Kleman says this analysis reveals the mileage for 90 percent of the vehicles is overstated.
"The EPA tests don't correspond to the way most of us drive," Kleman said. "Their tests represent driving on a 75-degree day on a road with no curves or no hills, which is ideal for maximizing fuel economy."
The EPA tests haven't changed in 30 years, so they don't take into account today's driving conditions. There's a lot more congestion, idling in traffic, and widespread use of air conditioning.
Consumer Reports runs its own fuel economy tests. The engineers say these tests—done outdoors—give a much more accurate assessment of the actual mileage you'll get from a car.
Consumer Reports' tests often turn up results that are substantially different from the EPA's—especially for stop-and-go city driving.
For instance the EPA says you'll get 22 miles per gallon with a Jeep Liberty diesel, but Consumer Reports found you'll get just half that—11 miles per gallon.
With a Chrysler 300 C, the EPA says you'll get 17 miles per gallon, but Consumer Reports' tests get only 10.
As for a Honda Odyssey minivan, the EPA gets 20 miles per gallon; Consumer Reports gets just 12.
The differences Consumer Reports turned up with hybrids in city driving are even greater. The EPA says the Honda Civic hybrid gets 48 miles per gallon; Consumer Reports measured just 26.
"Newer cars tend to overstate the mileage more than older ones," Kleman said, "so the discrepancy between what you're promised and what you're getting seems to be growing."
Consumer Reports says with skyrocketing gas prices, that's a trend that's more troubling than ever.
Yeah, poor maintenance is a problem. Cars are so reliable today that people never give a tune-up a second thought. They generally don't need it, but things do go wrong from time to time. A bad oxygen sensor or partially clogged converter can have a significant effect on mileage, but until the idiot light goes on, people are oblivious to the situation. Of course, not everybody is like this, but there are plenty of people that won't even get the oil changed every now and then.
I track my mileage with every tankful, since it is a very good indicator of when things are working properly or when something isn't quite right under the hood.
I know folks who drive with tires at 10 psi. I know folks who don't bother with an oil change til their engine runs dry. And then they need more than an oil change. Their idea of preventive maintenance is waxing the car. Sigh.
Hmm. Sounds like technology has become so advanced that even Cindy Sheehan can write about it.
The EPA "benchmark" is so far removed from real driving conditions as to be genuinely useless.
There is no air resistance.
The "highway" test is conducted at an average speed of 48mph.
Acceleration is limited to under 3mph per second. Vehicles with cylinder deactivation are tweaked to run the entire test on 4 cylinders.
"Vehicles are driven over identical driving patterns by professional drivers in controlled laboratory conditions on a dynamometer. Road forces and aerodynamic forces are fully accounted for in the test."
"The city test is approximately 11 miles long and is a stop and go trip with an average speed of about 20 miles per hour (mph). The trip lasts 31 minutes and has 23 stops. About 18 percent of the time is spent idling (as in waiting for traffic lights). A short freeway driving segment is included in the test. The engine is initially started after being parked overnight."
And the highway test: "The highway is a 10 mile trip with an average speed of 48 mph. The vehicle is started "hot" and there is very little idling and no stops."
While the city test doesn't seem too far off of reality, the highway test ought to be done at realistic highway speeds of 65 or 70 mph. Still, my results match up pretty well with what the EPA predicts.
I have the Toyota Prius, since November, and I am averaging overall about 48.5 in real world driving. It isn't as good as advertised, but twice my last car's mpg, and really fun to drive.
Late to the party here, but I can tell you I get significantly BETTER mileage than the EPA ratings. I'm supposed to get 19/26 in my Taurus and I get 23/32. Shove that in your pipe and smoke it, CR....
And I know several people who own hybrids, and not a single one of them averages less than 42 mpg (1 civic hybrid and 4 priuses).
Oh, and when CR comes out like they did yesterday and claims that the Mercury Mariner is one of the most reliable SUVs out there, but the Ford Escape and Mazda Tribute are not reliable, I say the standard deviation on their measurements is FAR too great to make any conclusions.
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