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Old 09-21-2005, 01:17 PM   #1
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"Real World" Fuel Economy vs. EPA Estimates

<p><strong>Publication:</strong>www.edmunds.com</p><p><strong>Date:</strong>05-11-2005</p><p><br>

<em></em>By <a href="http://www.edmunds.com/ownership/driving/articles/105503/article.html#">editors at Edmunds.com </a><br>
</p>
<p>Consumers tend to think that the large black numbers on a car's window sticker, which list the EPA estimated fuel economy rating, are what they will actually get while driving that car. Unfortunately, this is another situation covered by the saying, "Read the fine print." The fine print says, in essence, actual mileage may vary depending on a whole lot of things.
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What you as a car shopper need to know is that the gas mileage you get could be less. A lot less. Before you begin hatching some conspiracy theory involving oil companies, the U.S. government and carmakers, you should take a look at where these <a href="http://www.fueleconomy.gov/feg/how_tested.shtml">mileage estimates </a> come from.

The government puts a lot of time and care into testing for fuel economy. And these estimates provide important information for comparing two vehicles. What critics say is that, as part of the test program, a number of assumptions were made about driving habits. Those assumptions are now outdated; hence the discrepancy.

New vehicles are tested by the manufacturer according to guidelines outlined by the EPA. The EPA in turn reviews the results and confirms 10 percent of the test results with additional testing in the National Vehicle and Fuel Emissions Laboratory (NVFEL), in Ann Arbor, Michigan. The cars are tested by putting the drive wheels on a "dynamometer," a machine that allows it to simulate driving conditions while remaining stationary. The car is tested according to two different "schedules" to produce the city and highway ratings posted on a car's window sticker. (Fuel economy ratings are also included on the "Specs" page of all the cars on Edmunds.com.) The two schedules are meant to simulate different styles of driving that would be encountered in the two types of driving:

City: The test is started with the car's engine cold. The car then is operated in such a way as to replicate 11 miles of stop-and-go rush-hour traffic. Periods of idling are included in the test; average speed is 20 mph and top speed is 56 mph.

Highway: This test represents 10 miles of a mixture of rural and interstate highway driving. The engine is warmed up before the test begins and the average test speed of about 48 mph is maintained. The top speed reached is 60 mph. No intermediate stops or idling are included in the test.

The EPA acknowledges that test results might differ from real-world fuel economy ratings. It prescribes the difference to among other things the fact that the test cars are in optimal mechanical condition and thus perform better. But by looking at the EPA's testing procedure, it is clear that the habits of today's drivers are not duplicated. On most highways, speeds of well over 60 mph are common resulting in much lower fuel economy ratings. Furthermore, although the EPA tried to duplicate city driving by introducing periods of idling, today's congested roads produce far more prolonged stops. For a more accurate, and up-to-date reflection of the real-world fuel economy delivered by different vehicles, we invite you to look at the results obtained by Edmunds.com's long-term testing program.

At Edmunds.com an important part of our long-term testing program is recording "real-world" fuel consumption. Our <a href="http://www.edmunds.com/reviews/roadtests/longterm/index.html">long-term test vehicles </a> are driven by a different driver each month. Some drivers have a lead foot while other drivers are mellower. Over Edmunds' year of ownership (and typically 20,000 miles) these differences average out. Furthermore, each month, we record the best and worst mileage we have gotten.

We decided it would be interesting to pull out a sampling of different test cars that we have driven and compare the "real-world" figures to the EPA estimates. Hopefully, this will help you better interpret the numbers you will be seeing on window stickers the next time you go car shopping. We have included different vehicles to get the best possible cross section.

<table cellpadding="2" cellspacing="0">
<tr>
<td width="28%">Vehicle </td>
<td width="18%">EPA Estimate </td>
<td width="18%">Edmunds Average </td>
<td width="18%">Best Tank </td>
<td width="18%">Worst Tank </td>
</tr>
<tr>
<td width="28%">2004 Chrysler Pacifica <br>
(crossover) </td>
<td width="18%">17 City <br>
22 Highway </td>
<td width="18%">15.7 mpg </td>
<td width="18%">20 mpg </td>
<td width="18%">10 mpg </td>
</tr>
<tr>
<td width="28%">2004 Mazda RX-8 <br>
(sports car) </td>
<td width="18%">18 City <br>
24 Highway </td>
<td width="18%">17.1 mpg </td>
<td width="18%">22 mpg </td>
<td width="18%">13 mpg </td>
</tr>
<tr>
<td width="28%">2004 Nissan Quest SL <br>
(minivan) </td>
<td width="18%">19 City <br>
26 Highway </td>
<td width="18%">18 mpg </td>
<td width="18%">22 mpg </td>
<td width="18%">12 mpg </td>
</tr>
<tr>
<td width="28%">2004 Nissan Titan SE 4X4 <br>
(pickup) </td>
<td width="18%">14 City <br>
18 Highway </td>
<td width="18%">13.7 mpg </td>
<td width="18%">18 mpg </td>
<td width="18%">10 mpg </td>
</tr>
<tr>
<td width="28%">2004 Toyota Prius <br>
(hybrid sedan) </td>
<td width="18%">60 City <br>
51 Highway </td>
<td width="18%">41.2 mpg </td>
<td width="18%">54 mpg </td>
<td width="18%">31 mpg </td>
</tr>
</table>
<br>
As this table shows, the average miles per gallon for every vehicle recorded by Edmunds.com drivers was lower than the low end of the EPA's estimate. It is important to note, though, that the vehicles cited above were driven mainly on city streets and were often in stop-and-go traffic. Furthermore, the Edmunds.com average was based on a variety of drivers. A single owner, with a more conservative approach to driving, could easily improve these numbers.

This information shows that, while car shopping, you should assume that your fuel economy will, as the fine print says, vary depending on conditions. However, it is safe to say that your average will be on the low end of what the EPA is predicting. Proceed accordingly.

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Old 05-21-2008, 02:30 PM   #2
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Anybody who does not better the EPA does not know how to drive properly. I have never failed to best the EPA's estemate. Learn how to drive.
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Old 05-21-2008, 02:46 PM   #3
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This is extra, double, really-really true now, with the revised (lower) estimates. You have to be a Fast-n-Furious driver to not meet those.
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Old 05-30-2008, 09:52 AM   #4
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Quote:
Originally Posted by malherbe View Post
Anybody who does not better the EPA does not know how to drive properly. I have never failed to best the EPA's estemate. Learn how to drive.
QFT.

Rated at 34 top highway, pulling 36+ through driving habits alone (and not even aggressive hypermiling driving habits, just basic common sense stuff).
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Old 05-30-2008, 11:06 AM   #5
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All my life, it's been silly to think anyone could get up to the EPA numbers. It was just a firmly deeply held belief that those were pie-in-the-sky numbers and only useful for comparing one vehicle to another, not for estimating my actual fuel costs. Eventually I started actually paying attention to my FE and found that I could get about what the EPA said by driving way slower than normal people.

The new ratings may help a little, but you still have to be a kook like us or an incredibly slow driver (or both) to get those numbers. I still think that most people who aren't speed demons still don't manage to hit the EPA estimates.
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Old 06-02-2008, 10:00 AM   #6
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Quote:
Originally Posted by theholycow View Post
All my life, it's been silly to think anyone could get up to the EPA numbers. It was just a firmly deeply held belief that those were pie-in-the-sky numbers and only useful for comparing one vehicle to another, not for estimating my actual fuel costs. Eventually I started actually paying attention to my FE and found that I could get about what the EPA said by driving way slower than normal people.

The new ratings may help a little, but you still have to be a kook like us or an incredibly slow driver (or both) to get those numbers. I still think that most people who aren't speed demons still don't manage to hit the EPA estimates.
It helps to employ that other favorite of high gas mileage and plan out your route to accommodate your speed. The back roads I've been traveling since last week have a max PSL of 55 mph. Which makes going 55mph seem an act of being a Law Abiding Happy Citizen and not the act of being a Fringe Radical Extremist Kook, like it seems we're viewed on the interstates.
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Old 06-02-2008, 11:23 AM   #7
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The old epa tests seemed pretty reasonable to me. My wife driving the Odyssey averages about 21mpg - it's rated 21 combined. Park the cruise at 70mph - 25 mpg, just like its rating. Last week I took a 600-mile round trip on the highway with 6 people and camping gear and AC blowing. With careful footwork between 60 and 65mph, I averaged 28mpg.

In my civic, before I was hypermiling, I had a best highway tank of 40mpg (rated 38) and I averaged in the low 30's for daily driving (it's rated 33 city).
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