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  1. #1
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    Mileage Disagreement

    I have an 08 MMH and I drive a lot. I have about 6500 miles on the car in my first couple months. On my last 3 or 4 tanks of gas, I noticed that my actual calculated gas mileage was noticeably different that the NAV display. They have been very close until now. I have actually tried to use the same pump at the same gas station to keep the “full” gas tank level somewhat consistent. The actual mileage has been consistently 3 to 4 mpg less than the display. I probably averaged about 31 mpg (I drive a lot of highway miles) on my NAV and actual calculation since I have had the car. Now, the NAV still gives me 31-32 but my actual mileage is much less. In fact, I have run out of gas twice (50 miles past “0 miles left” used to be pretty safe). I don’t have a problem with the reduced mileage, I attribute this to the air running more at this time. Is there any way to offset the NAV mileage? Sorry for the long story, any ideas?

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  3. #2
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    From reading other posters who have the hybrid/navigation system in their vehicle, it is common for this system to slightly overstate the true mileage. If I remember correctly it is some where between 1-2 mpg on the average. Most of this information comes from the www.greenhybrid.com site.

    Many posters have stated when your vehicle states you are out of gas (0 miles to empty), the vehicle still has 1.3 gallons in the tank! It is believed Ford did this in an attempt to minimize out of gas episodes. If you got 50 miles past 0 miles to empty and you are averaging about 31mpg, then this experience further credits the belief your tank has 1.3 gallons left when it reads 0 miles to empty. However, why would one drive past this reading? Maybe you can explain this?

    Your gas gauge is inaccurate. It drops too fast from full. Many posters have stated this.

    Lastly, many posters have purchased a scangauge II unit to provide feedback for economy and vehicle operations. I have also done the same.

  4. #3
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    Mileage

    Well, as far as going past the mark. I happen to think people buy hybrids because they are conscious of gas mileage. I think it is silly that we need an early warning system to tell us we are out of fuel when we still have something like 10% of capacity left (topping off). If that is the case, make the tank smaller?? Why not fill up every 10 gallons then. My point is, we have a 15 gallon tank, why not use it. I would rather it be bigger. At 30+ mpg, you should be somewhere on the order of 450 mile per tank. Like I said, sometimes the NAV is right on the money with actual mileage. Two tanks ago it was actually 0.6 lower than actual. But this morning it was almost 3 mpg lower. That has a huge affect over 15 gallons. Are you saying that the scan gauge give more reliable data than the NAV?

  5. #4
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    In fact, I have run out of gas twice (50 miles past “0 miles left” used to be pretty safe).

    This is the red flag for me, if you were consistently going more than 50 miles past 0 MTE, in my FEH that would be over 40 MPG....

    I have the Average Econ display, the Navi Display, and a SCII. If the speed is calibrated in the SCII to match the odometer, the Average Econ MPG readings are nearly identical to the SCII, but the Navi reads consistently higher. It does seem that the Average Econ scrolls data off about halfway through the tank, and it appears the Navi unit does the same. Also, the MTE calculation seems to use more than just the current Average Econ reading, because I have had the Average Econ pegged at 99.9 MPG after a fill-up, but my MTE was still only about 490, not the 1000+ I was hoping for....

  6. #5
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    Well, I dont' want to split hairs here. Depending on how full you fill the tank, you can get to the point where there is something like 1.4+ gallons left at the 0 miles left mark. I didn't mean 50 literally... more like 40-45. I am just aggrevated that here I think I am using good driving habits to get 31-32 mpg (per NAV) and really it ends up being 27 or so. I mean, what's the point of having it if it can be off by that much. Every tank it get the same thing on the NAV 31-32ish but it reality it has been ranging from 27 to 31ish (more often the 27ish).

  7. #6
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    I just saw your last comment DesertDog.. nice! I would be happy with 450 though! So the SCII does = actual gas mileage based on gallons at fill up and odometer?

  8. #7
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    You have to input some data into the scanguage II when you first buy it. There is some reading involved and then it becomes pretty much automatic and a lot of information is at your fingertips including "gallons used" and "miles to empty".

  9. #8
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    Quote Originally Posted by DesertDog View Post
    [I]

    I have the Average Econ display, the Navi Display, and a SCII. If the speed is calibrated in the SCII to match the odometer, the Average Econ MPG readings are nearly identical to the SCII, but the Navi reads consistently higher. It does seem that the Average Econ scrolls data off about halfway through the tank, and it appears the Navi unit does the same. Also, the MTE calculation seems to use more than just the current Average Econ reading, because I have had the Average Econ pegged at 99.9 MPG after a fill-up, but my MTE was still only about 490, not the 1000+ I was hoping for....
    Carl, the SG11 calibrates speed in percentage points + or - and doesn't use decimal points. My OD miles are 1.7% higher than the SG11. I went ahead and increased my speed on the SG11 to 2%, what do you have yours set at to match your OD?

    Anyone else calibrate their SG!!?

    GaryG

  10. #9
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    Mine is 4% currently.

  11. #10
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    Quote Originally Posted by ve7tcc View Post
    Mine is 4% currently.
    Interesting, but how did you come up with 4%? I thought 2% was .3% over my results in 650 miles. I'm going fill up early and reset my trip, Tank and nav sys MPG average and keep a eye on it. I expect the nav system to drop data at about 200 miles, but I looking at the trip and the SG11 tank miles. BTW, I had many tanks where the nav sys was lower than the SG average because my mileage was worse at the end of the tank.

    GaryG

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