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#1 2007-10-16 22:42:56

Anonymous
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Registered: 2007-10-16
Posts: 1

Unadjusted Highway EPA MPG?

What does "Unadjusted Highway EPA MPG" mean in the vehicle MPG spec?

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#2 2007-10-17 17:00:19

support team
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Registered: 2007-06-20
Posts: 188

Re: Unadjusted Highway EPA MPG?

Here is how manufactures test their vehicles - they put a vehicle on a special machine called a dynamometer and a professional driver simulates typical trips for city and highway driving. If your state has requirements for vehicle emission testing - you surely have seen dynamometer before.

Then same way as during emission testing - they connect a hose to the vehicle tailpipe to catch the exhaust. By measuring carbon in the exhaust gases manufactures calculate [b]unadjusted MPG rating[/b].

[b]Unadjusted city EPA MPG[/b] is calculated when driver simulates typical city driving, and [b]unadjusted highway EPA MPG[/b] is calculated during highway driving simulation.

Estimated city MPG is calculated as 90% of unadjusted city MPG.
Estimated highway MPG is calculated as 78% of unadjusted highway MPG.

So assuming ideal driving conditions and driving style - you should be able to see your vehicle's actual MPG reach to unadjusted MPG values.

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#3 2009-05-29 11:54:15

Treven
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Re: Unadjusted Highway EPA MPG?

I don't think they use a dynomometer for MPG figures.  I think they always use a test track.  Wind resistance at hwy speed are the biggest use of fuel and there is no way to account for that on a dynomometer.

#4 2009-06-01 12:21:00

support team
Administrator
Registered: 2007-06-20
Posts: 188

Re: Unadjusted Highway EPA MPG?

Dear Treven,

Below is the quote from _no_links_www.green-car-guide.com/news/official-mpg-v-real-life-mpg.htm

[quote]The tests themselves are conducted on a ‘Rolling Road’ dynamometer and have two parts...[/quote]
So the tests are actually run on a dynamometer and not on the road. And you are absolutely correct, those tests and unadjusted MPG values do not account for vehicle aerodynamics, etc. However it would be difficult to run any tests on open track because of the wind, outside temperature and many other factors would affect the MPG values and it would not be possible to get same reading even the next day.
Our understanding is that what adjustment is for - to get those unadjusted dynamometer values closer to real-live values.

Thanks for your post and have a great week!

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#5 2010-03-17 16:26:55

bob
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Registered: 2010-03-17
Posts: 1

Re: Unadjusted Highway EPA MPG?

[quote=Anonymous]What does "Unadjusted Highway EPA MPG" mean in the vehicle MPG spec?[/quote]

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#6 2010-03-17 16:38:57

support team
Administrator
Registered: 2007-06-20
Posts: 188

Re: Unadjusted Highway EPA MPG?

Dear bob, I'm not sure what you are asking, please read this topic from the top to find out what unadjusted MPG values are.

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#7 2010-05-21 02:16:22

Jerry Powers
Guest

Re: Unadjusted Highway EPA MPG?

[quote=bob][quote=Anonymous]What does "Unadjusted Highway EPA MPG" mean in the vehicle MPG spec?[/quote]
[/quote]

#8 2010-05-21 11:58:10

support team
Administrator
Registered: 2007-06-20
Posts: 188

Re: Unadjusted Highway EPA MPG?

Dear Jerry Powers and Bob,

We have made a few changes to our original post and highlighted the definitions. We hope it makes a bit more sense now.

Thanks and have a great weekend.

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