• Aug 31st 2009 at 7:00PM
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2010 Toyota Prius – Click above for high-res image gallery

Ever wonder what actually goes into determining the rated fuel economy of a new car or truck? Anyone with a vehicle that's failed to live up to its EPA estimated figures would surely fit into that camp – especially if the car or truck were purchased in large part to its high mileage rating – and you can add our names to that list as well. As it turns out, the process is every bit as as complicated as we'd expect.

Car and Driver recently hung out at the EPA's testing facility near the Motor City, and some highly intriguing bits of information were gleaned. For instance, C/D says that just 15 percent of new cars get tested by the EPA each year for fuel efficiency, and the rest get their ratings from testing performed by the manufacturer using the government agency's guidelines. It's reportedly rare that the EPA's figures vary greatly from the numbers provided by the manufacturer, but if they do, discussions and negotiations ensue.

There are a total of five tests performed to measure expected fuel efficiency, some dating all the way back to the late Seventies. More recent protocols are a bit more complex and require specialized facilities that can cost up to $10 million dollars by EPA estimates. There's plenty more to the story, so click here to read the full four-page report. Hat tip to Julio!

[Source: Car and Driver]

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    • 1 Second Ago
      • 6 Years Ago
      "and the rest get their ratings from testing performed by the manufacturer"

      Ah-Ha! Now we know where Ford got 41 MPG for the Fusion and 25 MPG for the SHO...they made it up.
      • 6 Years Ago
      From the article, "Don’t even think of comparing EPA figures with stand­ardized fuel-economy tests from other countries because the test cycles are very different. For example, the European highway rating, called “extra urban,” is higher than the EPA’s by about 30 percent, so a rating on that cycle of, say, 60 mpg, would be closer to 40 in this country. The mainstream press, not realizing the difference, often complains that automakers refuse to bring efficient models here when, in fact, they may not be all that efficient when measured by U.S. standards."

      Autoblog is guilty as hell of this, hardly a day goes without another pointless post about the miraculous mpg achieved by some European eco-cheesebox
        • 6 Years Ago
        Example please? If they are always doing it you should have no problem.
      • 6 Years Ago
      This argument gets old. Hundreds of thousands of miles of road and equal or more drivers makes "actual" about as accurate as WMDs in Iraq. What really works on the EPA's site is the ability to place YOUR actual fuel economy numbers. As a base line, the EPA does well and YOUR driving will certainly make a difference. Journalist playing scientist make for lousy control substances. Bless your hearts C/D.
      • 6 Years Ago
      Hills. Hills. Hills are definitely not on any EPA test route. My guess is they never have been. All my years living in the San Francisco Bay Area has definitely made that clear. Hills kill mileage in a way never referenced by their testing. Still -I've had a lot of cars and their numbers are perfectly usable for comparing one model against another. The ones ranked super efficient by them... were. The ones that weren't ... weren't.
      • 6 Years Ago
      EPA, MPG, Blah, Blah, Blah the Prius is still ugly...
        • 6 Years Ago
        All I said was that the Prius is an unattractive vehicle. I never said it didn't sell, or that it wasn't innovative. I have no idea what "constant crowing" you are talking about, it sounds to me like you are trying to argue for the sake of arguing.

        I'm sorry if you own a Prius and I offended you by my comment that they are UGLY. Get over it tough guy.
        • 6 Years Ago
        The still sell, just don't buy one. Your constant crowing about how your useless opinion somehow means something to someone who acutally cares. STFU tool.
      • 6 Years Ago
      I read that C/D article and I was absolutely freaking appalled and how archaic and irrelevant the EPA tests were, and even more disappointing was just how little effort (and money) the EPA puts into testing cars at all.
      JDM Life
      • 6 Years Ago
      I hate the color of that pruis soooo much it just scream elderly.
        • 6 Years Ago
        @JDM Life
        Seriously, all the more I would like to submit that car to "will it blend?"
      • 6 Years Ago
      The MPG sticker doesn't account for poor driving (stepping on the gas so you can slam on the brakes at the next red light). It does help to make a comparison, since if car 1 gets 25mpg combined and car 2 gets 27mpg combined you know that car 2 will get you a cheaper gas bill. My car is rated 18/26 and I get mid 24's in stop and go traffic. When I go long distance at highway speeds, i've gotten low 29's. The MPG rating is for comparisson, they'll never be able to replicate every driver's style of driving.
        • 6 Years Ago
        "It does help to make a comparison, since if car 1 gets 25mpg combined and car 2 gets 27mpg combined you know that car 2 will get you a cheaper gas bill."

        You know no such thing. There are so many apples to oranges ways to game the test that it no longer shows much of anything. In the 90s when gas was almost free and there was no reason to build to the test, yeah. But today it's a contest of test specific fuel mapping and shift programming.

        Compare EPA sticker numbers against Consumer Reports testing on real roads and it's clear that EPA's numbers aren't even worth reading.
      • 6 Years Ago
      I thought 10 M$ was chump-change for EPA.
      • 6 Years Ago
      A pretty good article, all in all.

      One note, the Panamera won't be the first start-stop non-hybrid car in the US, just the first one in a while. Start-stop came and went in the 80s in the US.

      And speaking of that, what start-stop is going to do to fuel economy figures is a crime. The UDDS (LA-4) includes far too much stopped time. Start-stop is going to greatly inflate city mpg figures in a way that typical drivers will never, ever see. And on top of this, non-hybrid start-stop sucks sufficiently badly that most drivers won't even turn it on.

      Also, the mpge figures really should be corrected before allowing companies like Tesla to sell CAFE mpg credits gained by their inflated figures.
      • 6 Years Ago
      The biggest problem I have with this is the way CAFE has been sales weighted.

      One manufacturer can beat the mileage of all other manufacturers in every car size category, but have a lower CAFE average because they are very successful in trucks. While I agree that there has to be some sort of sales basis so companies don’t make one $1,000,000 super efficient car to be in compliance, it still seems over sales weighted. The system forces car makers to sell small cars below costs to offset their average.

      For example: Chevy is now beating the mileage of Toyota in nearly every size category, but has a lower CAFÉ average. Toyota sells a lot of Corollas, while Chevy sells a lot of Silverados. Ford is moving in that direction too.

      I hope the new categorization starts rewarding makers for being efficient in a given category.
        • 6 Years Ago
        It's not a problem for CAFE. It's a problem for Chevy.
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