Here is a piece of the pie.

Mass Air Flow is used for (part) of the MPG calculation.

When using ethanol, the amount of fuel per mile goes up ( MPG goes down ).
But the amount of AIR pulled into the engine changes very little.

Thus, the calculated MPG on the Nav changes very little.
But your gallons pumped will show lower MPG.

That's not all, but that's part of it.

HTH,
-John

P.S. When using high levels of ethanol, this increases available power, and thus with the eCVT my RPM's are lower at the same road speed. Thus, the air-flow is lower, and the calculated MPG is higher. Needless to say, the fuel trim is high with high ethanol, thus real MPG is lower.

I have proven that the ScanGauge does not use fuel trim as part of the MPG calculation. I'm still not sure about the on-board MPG.

 

Thanks for all the help. The 4% over seems right on. Can (will) Ford recalibrate this?

 

So is ~3mpg the expected decrease when E10 is used? My state just switched to E10 and I've gone from ~31MPG to ~28MPG.

 

It shouldn't be that big of a hit, but that is what most people report, so your car is behaving normally. I'd say mine loses 3 MPG also.

However, the curve is not linear. I usually get 25 MPG with 85% ethanol.
( 85% not recommended by Ford, but once you are past the powertrain warranty period, feel free to experiment... dozens ( 100's? ) of people have, and without ill effects )

 

From what I've seen with my 2008 FEH and E10, ~3MPG is fair.

I know of four stations in my entire state that still have and advertise 100% gas (the closest being about 110miles from home base). Just so happens that I stopped by that one today and topped off my half empty tank with ~6.5 gal. I reset the NAV FE and trip odometer and proceeded to drive ~150 miles of 95% Interstate and the NAV display was right at 39MPG when I got home. There was some A/C usage and window down time. Speeds were 60-80MPH on slightly rolling hills but the last 30 miles were in the rain and most of the trip was with gusty winds. (I do feel like 39MPG was about all that I, myself, could have gotten today without slowing down more and I wasn't willing to do that).

Compare that to the 32MPG (logged and calculated) I have gotten over the first 33,000 miles with almost exclusively E10 and about a 50/50 split. I'd love to get a full 100% gas tank but it never seems to work out that I'm near one of the four stations when I have an empty tank.

Greater minds than mine have debated what should happen with E10 and FE but I continue to see 10%+ improvements in FE every time I get less than an E10 mix in the tank. Even if the effect is all placebo/mental, I still LOVE the end result!

P.S. 100% gas was $1.85/gal, same or slightly cheaper than other E10 pumps in the same area, right off the Interstate.

 

My experience: I have a 2008 MMH and have averaged 32.04 MPG for 21,520 miles. I am a conservative driver but not a hyper miler by any stretch of the imagination. My highest tank was 39.9 MPG and my lowest tank was 25.5 MPG.

As has been mentioned by others, fuel economy on these hybrids seems to take a bigger hit in cold weather and in high speed driving than in non-hybird vehicles (both elements were factors in my low 25.5 MPG tank). I have also noticed that the computer calculated average fuel economy is about 5% higher than the actual calculated at fill up time.

Overall I am very pleased with my MMH and would buy another one. I wish I had waited for the 2009 model so that I could drive 40 MPH in EV mode rather than 30 MPH. That 10 MPH difference would allow me to drive in EV mode much much more than I currently can.

 

My 08 FEH and 08 Focus are both reading app 3.5-4% higher than actual. When I questioned this with service manger his response was, Ford wont recalibrate unless it is more than 10% off.

Hopefully when things pick up from part time to full time I can purchase couple of SG for both vehicles.

One complaint i have with FEH is when ICE is off at real low speeds you can hear front noise, maybe some lub is needed.

 

my 05' feh averages about the low 30's through out the winter, high 30's in the summer. i live in the northeast, where we get the wind chill. which can lower the mpg's. i think were running e10 here. i use the factory nav for mpg readout, but i never think to check the mpg's by hand . i have 95,550 on my 05'. it's about time for it's first scheduled tune which may increase the mpg's.

 

gpsman1: In your above post you state that power goes up with higher ethanol content. What's the mechanism?

 

We all know ethanol is an excellent fuel for high compression engines.
But what about the FEH with lower compression?

Well, I have a guess...

A) more fuel per stroke is being injected
B) ethanol burns slower, and thus it is said, more completely than gas
C) more fuel would mean more atomized or vaporized droplets, meaning more surface area in contact with the air during combustion, perhaps leading to more combustion, and more power per stroke.
D) ethanol has fewer btu per gallon, but if a greater % of useful energy can be extracted, then the MPG decrease will be minimized, and/or the power maximized.

My observations from the "outside" of the engine:
Lower RPM in general with high % ethanol
Lower RPM climbing hills
Steady RPM when climbing hills with Cruise Control on.
Slightly "higher MPG when towing with E85 in the tank.

No joke. Last September I towed a 2000 lb. trailer over the Rockies and got about 23-24 MPG* at 55-60 MPH with a high percentage of ethanol in the tank.

Last week I towed 2600 lbs. and got 19 MPG* with a mix of regular gas and E10. I know the trailers were not identical, but the data is convincing to me.

It sure leans towards me getting more power out of the ethanol.
*Hand calcs based on gallons pumped. The ScanGauge and the dash don't calculate MPG properly with ethanol in the tank, especially when changing fuel blends, and I do since I travel all over the mid-west for work ( & play ).

P.S. The 2000 pound trailer had a greater frontal cross area than the 2600 pound one.
The 2000 pound one was 7' wide by 7' tall. The 2600 pound one was 5' wide by 7' tall.