I have a 2009 FEHL. I do not have a ScangaugeII. I have kept accurate records of fuel purchases for 5700 miles and I am getting 31.8. Not great but it is creeping up and it's 50% better than the old Dodge. When I don't need the map, I keep the mileage bars on the screen that graph the last fifteen minutes. The "average gas mileage" is always between 34.3 and 34.8. Whazzup? Is this Ford marketing? I know it is just for the last fifteen minutes but I have been checking it ever since I realized the descrepancy and it is ALWAYS 34.*. Any clues?

 

It's winter here and there are days I'm lucky to get 10 mpg for short trips, even tho I use a block heater at night. My best Interstate trip (65-70 mph) this month was 22 mpg. Most of the last 30 days was below zero. Consider yourself very lucky, even if you don't have a SG.

 

I stated my euphoria at getting gas mileage that was 50 % better than the old Dodge. My question is why does the "average MPG" number on the info screen of the nav unit overstate the actual mileage by 3 MPG?

 

If the NAV is getting information on actuall fuel flow and the number of times the wheels roll around, it should be able to calculate the actual gas mileage regardless of the nature of the fuel.

 

nope, the nav has a preset calculation programed, it has no way to tell if you're using straight gas, or e10, or anything for that matter. Search around like stated above and read up, then you'll understand.

 

A number of us '09 FEH W/Nav owners have been comparing pumped gas to the Nav MPG average readings since our purchases. It appears the Nav system MPG average is about 4% higher than real MPG. See this thread for details:
https://www.greenhybrid.com/discuss/...45/index3.html

Your guess as to why Ford has this problem with the Nav system is as good as mine. Not only does the Nav system have problems with the correct MPG, but the SGII has an even higher percentage off than it. So far I'm up to adjusting my SGII's to 13.3% so 4% is not as bad. The area of the problem in my mind is measuring Fuel-Cut (DFSO) correctly. Prior FEH/MMH models did not have the aggresive fuel-cut during deceleration like the '09 FEH does. I think now that I have both my SGII's adjusted to near the correct MPG average, I'm going to start adjusting fuel-cut from 17 to lower numbers. I already adjusted the default setting of 24 to 17 and found no change in MPG average readings. If I see a change in the new lower Fuel-Cut settings, I may confirm the real problem.

GaryG

 

Julian, I deleted my "quick answer" because life just isn't that simple. If the NAV average MPG was off because of 10% ethanol as I suspected, the discrepancy should increase when higher concentrations of ethanol are used in the fuel. A wise poster named gpsman1 did not observe the expected discrepancy when he used e85, and nobody seems to know exactly how the NAV calculates mileage... unless I missed something in my thread search.

The ScanGauge however, does assume you're using 100% gasoline in it's MPG calculations, and one has to adjust the fuel trim accordingly.

The fact that the NAV displays innacurate MPG data is the best evidence that the NAV does not get actual metered fuel flow data. Since there is no fuel flow meter as such, the fuel use has to be estimated based on other data. (Okay, there's a chance that the NAV could collect all of the injector pulse-width data to meter fuel used, a huge amount of data, but my gut says they don't do it that way.) The engine does however measure the mass of the air entering the engine (MAF) and this info could be used to extrapolate the fuel used.

Many words to say "I don't really know"

-J

 

I have over 31,000mi on my 08 FEH and I consistently see about 2MPG less than what the computer says when I calculate using the distance/pumped amount.

It's been reported that there is a data retention limit issue on the pre-09 models that causes it not to track a full tank's worth of data. I don't think the '09 model has this limit so that shouldn't be your issue.

E10 may be the culprit. It's been so long since I didn't have that in the tank that I can't confirm this.

 

E10 does not effect the MPG readings on my '05 FEH Nav or the SGII so I don't think E10 effects my '09 FEH. Also, when I changed from straight gas to E10 in my '05, the MPG reading were always lower not higher on both the Nav and SGII.

GaryG

 

I am in Toronto, Canada. I drive a 2008 4WD FEH.

In summer we have 25 C / 76 F temperature, and I got 7 L/100kM (33.5 MPG) on my display.

Now we have -12 C / 10 F temperature, and I got 9 L / 100kM (26 MPG) on my display.