Mileage Disagreement
Created July 18, 2007, at 11:28 am by jdnels
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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2 years ago
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 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.:)
2 years ago
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?
2 years ago
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....
2 years ago
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). :)
2 years ago
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?
2 years ago
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". :)
2 years ago
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
2 years ago
Mine is 4% currently.
2 years ago
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
2 years ago
So far, I only put 49.9 miles on my trip OD and the SG11 tank reading would increased to over the 3.9 miles over 650 miles. This confirms a 2% increase adjustment to the speed of the SG is to much. A 4% adjustment would put the SG near 8 mile over the dash trip OD in 650 miles. This all means the SG needs programming to allow decimal points in the percentage of speed.
Carl? Please tell Ron of my findings.
GaryG
2 years ago
I set my scale factor to 1%, when in reality it is closer to 1.5%. I have another revision of the new SG firmware, but I haven't checked the calibration. I suspect it is still in whole number increments, though. When I report back to Ron on the latest firmware, I will mention it to him.
With the new firmware in place, I can monitor SoC to the hundredths. Also, battery temp, charge/discharge limits, delta module voltage (always zero so far), and a ton more.
On another note, I noticed during my last tank that the navi MPG actually dropped below the message center for a while. I noticed that even hundreds of miles into a tank, I can affect the navi reading much more easily than the message center average econ reading. I'm thinking the navi must use some form of weighted moving average to calculate the average MPG
2 years ago
All this sounds great Carl!
I've got over 100 miles on my FEH after setting the speed at 2% over on the SG11. The SG11 is .1 miles over every 15 miles now, but much better than the default setting. In addition, the SG11 is now tracking the navi MPG much better. This will change when the navi starts dropping data though.
Most people report that the navi reads higher than the SG, but if I start getting better mileage, the SG can reads lower than the navi because it averages the entire tank. The fact that the SG11 default speed setting is to slow, makes the navi seem over the correct mileage.
It appears from what Carl noticed with the message center econ gauge, that it holds data longer than the navi MPG average.
GaryG
2 years ago
An Update:
After the 2% adjustment in the speed of the SG11, here are my present readings:
Navi
44.5 MPG Avg.
Dash
169.3 miles trip OD
MTE 417
SG11
44.6 MPG Avg
20mph Avg.
24.9 hrs
8.1 hrs
499 TTE
170 miles
11.2 gal TTE
3.8 Gal used
Notice how close the miles traveled and the MPG averages are at this point with the navi, dash, and SG11. I ran the cabin A/C more right after fill-up, so I expect the navi to start dropping that data soon and show a higher average than the SG11.
GaryG
2 years ago
Another Update:
Something very interesting happen yesterday I've never noticed. My navi MPG average started breaking away from my SG11 tank average as always, but I noticed it was tracking the SG "Today" average with every tenth of a mile.
I quoted my self so everyone could compare my readings from the beginning of this tank below. Newer Reading:
Navi
46.3
Dash
trip 354.1
MTE 254
SG11 - Tank
45.9 MPG average
22 MPH avg
15.0 Hrs TTE
16.0 Hrs
330 miles TTE
357 miles (now 3 miles over dash trip)
7.2 Gal TTE
7.8 gal
SG11 "Today" average
46.4 MPG avg
25 MPH avg
52 MPH max
4.5 Hrs
2883 RPM Max
112 miles
181 FWT max
2.4 Gal
GaryG
2 years ago
This is my third and last post on this tank after changing the SG11 default speed setting to plus 2%. Filled-up today and got these numbers before resetting.
Nav
46.8mpg
Dash
trip 635.3
MTE - 0 @ 604 miles (31.3 miles past zero)
SG11 - Tank
45.8mpg average (Final Tank)
22 MPH average
2.2 Hrs
28.5 Hrs
50.3 TTE
640 miles (4.7 miles over Dash Trip OD)
The SG11 Tank Trip default setting was 1.7% below my Dash Trip OD miles. Changing the speed setting to plus 2% put the miles over by .74% (4.7miles over 635.3 miles). If you take the dash trip OD (635.3) and divide that by the SG11 tank gallons used (13.9), I got a 45.7mpg average on this tank. BTW, I added 14.09 gallons at the pump.
GaryG
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