"Your mileage will vary"

[ivymike]

I have a 2012 Ford Edge Limited with 3478 miles on it. The EPA fuel mileage sticker puts the fuel economy at (cty/hwy) 19/27 mpg. My experience has been very different from that, and I'm wondering whether this is something that is likely to resolve itself, or if the mileage estimate is simply WAY wrong for the vehicle.

Below are my records of mileage and fuel economy since purchase:
date odometer gallons [mpg tank]
21-Apr-12 280 0.000
27-Apr-12 482.6 12.250 16.5
1-May-12 746.9 14.236 18.6
7-May-12 916.5 10.410 16.3 17.3
11-May-12 1120.7 12.969 15.7
14-May-12 1365.2 13.616 18.0
21-May-12 1594.3 12.183 18.8
30-May-12 1803.3 13.114 15.9
06-Jun-12 2022.5 13.061 16.8
11-Jun-12 2212.2 12.226 15.5
16-Jun-12 2437.1 13.969 16.1
22-Jun-12 2613.4 12.230 14.4
02-Jul-12 2797.6 13.491 13.7
07-Jul-12 2955 9.553 16.5
08-Jul-12 3131.7 8.696 20.3 (purely hwy)
08-Jul-12 3294 6.723 24.1 (purely hwy)
14-Jul-12 3477.5 12.256 15.0

I have been using 87 octane fuel, as per the recommendations of the manual, and I have not been driving in any particularly interesting fashion, save for the tank consumed on 08-Jul-12 where I drove the entire time on cruise control at speeds between 55 and 70 mph (depending on the local speed limit) and managed to get 24.1 mpg. The rest of the driving is suburban, with a mix of highway and medium-distance stoplight driving (40mph+ speed limits are typical in our neighborhood)

The speedometer reading precisely matches GPS readings of speed, so I assume that the odometer is also calculating miles correctly. The tires are properly inflated (actually 1 psi higher than what it says inside the driver's door frame, or 33.5 psi).

So what gives? I can't get 27mpg out of the vehicle unless I drive at a constant 40mph on flat ground (and then it says I'm getting about 27.8)! What cycle would I possibly drive it on to average 27 mpg highway?

 

[NormPeterson]

As the brand-newness begins to wear off, you may be driving it just a little more "enthusiastically".

If it's a throttle-by-wire arrangement, the ECU may be following this and opening the throttle plate a little more aggressively than it did in the beginning with nothing to go on.


Norm

 

[swall]

It is my understanding that the EPA mileage tests are conducted with standard gasoline,i.e. no ethanol. Nearly all gasoline in the U.S. has up to 10% ethanol these days, so you are starting out with a 5% mileage penalty when you compare real world mileage with the EPA figures.

 

[patprimmer]

My sums showed 10% ethanol as 3% less energy content, but it was a while ago. Maybe I am miss remembering.

Regards
Pat
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[swall]

Yes, 3% is correct. I incorrectly remembered 5% from thread 71-31230

 

[rmw]

I think 3% less energy would end up as as just about 5% less mileage after vehicle losses, wouldn't it?

rmw

 

[NormPeterson]

I doubt most people drive consistently enough for the difference between 3% and 5% to really matter . . .


Norm