Odometer and Trip Odometer off by 110 miles per tank

Highspeed005 · **Joined:** Thu Apr 11, 2013 1:48 pm **Posts:** 13

Hey guys, I'm new to the forum and had a question about the odometer readings. I check my MPG after every fill up simply by taking the trip odometer, which is zeroed every time I fill up, and dividing by the gallons of gas put into the tank at my fill-up. Today was 196.6/8,3 gallons which = 23.68 with my GDE Eco Tune.

I also use an Application on my phone to calculate my MPG, but the app requests my odometer reading. Between fill-ups, my odometer read that I drove 251 miles. That math looks like this, 251/8.3= 30.24.

Betty, as I've named her, has standard tires and no upgrades. I didn't own Betty long enough to test her MPG Pre-Eco Tune.

A few points, and a few questions.

Points: I really like the idea of telling people that I get 30mpg mixed city and highway driving, but I am relatively sure it isn't true. Even Keith at GDE said that he guarantees 3-5% improvement in MPG which would put me at around 27.3MPG on the highway. That math is here: 26 MPG being the sticker quoted MPG... 26*5%=1.3 ... 1.3+26=27.3.

If my standard OD is off by 110 per tank, that's about 3000 miles per year ADDED to the OD which means by 2005 with 146k miles actually may only have 125k? (22MPG = 27 Tanks per year @12,000mi per year over 7 years). Not to go skeptic, but is this a car manufacture creation? I don't want this to turn into a conspiracy theory thread, but just a thought.

I am happy with my GDE Eco Tune, but be warned, anyone claiming 30+MPG should check use their trip OD, standard OD, AND GPS OD before claiming 30mpg.

Questions: Is this normal? Has anyone else had this issue? Anyway to fix this?

Sorry for the repost; just trying to get some answers.

car0430a · **Posted:** Tue Apr 16, 2013 11:23 am

Ok and hello there first I'd like to say I hope you did not put gas in your fuel tank. Sorry has to say it.
I had once thought and still do think my odometer reads off on occasion. As I just drove from Hastings Mn to Janesville Wi I noticed that my trip odometer was only off by 1-5 miles as I compared to google maps and the iPhone app. After reading your post I am a little confused as to how you put milage in from hand calculations and your app but came up with different miles as you stated you got them both from your odometer. Or as I read into it your saying your trip calculator is not accurate to the actual odometer. I will have to write down my actual odometer and compare on way home this evening.

skates04 · **Posted:** Tue Apr 16, 2013 12:10 pm

Compared to my Garmin GPS my Odometer is short by 9.8%. I do run a larger 265/75/16 tire so my difference some what makes sense. Your best bet is to compare to a GPS so you get rid of the variables of the fact the odometer is off from the factory and tire size.

papaindigo · **Posted:** Tue Apr 16, 2013 12:53 pm

Just to get consistent terminology on the table:
1. speedometer - mph; may be off +-5% or worse if you are running tires with diameter that's different from OEM
2. odometer - cumulative miles traveled since the vehicle was put on the road; may also be off like the speedometer but since IIRC it's feed data from a different sensor the error may be a different amount and/or direction than the speedometer error
3. trip odometer adjacent to the in dash odometer - miles traveled since last zeroed which "should" be similar if not nearly identical too the difference between the current odometer reading and the odometer reading when the trip odometer was last zeroed.
4. EVIC (overhead console) lists decreasing miles to go until next service (can be manually reset to zero); trip miles which may or may not automatically set when you fill up (I honestly have no clue); and mpg. Exactly where that data is derived I don't know but I've never seen any real good correlation between EVIC mpg and actual mpg and have never paid any attention to the miles that the EVIC shows. EVIC mpg is notoriously inaccurate with or without a GDE tune.

To check speedometer, odometer, and trip odometer accuracy or lack of accuracy you need to do a GPS monitored run of at least 25 miles ideally on a relatively flat and straight road. Adjust you speed and mpg calculations accordingly. NOTE true mpg can only be calculated by using the same pump at the same station and filling the tank to the same level every time (e.g. clear unfoamed fuel at the filler neck).

If some combination of the speedometer, odometer, and trip odometer are wildly off it's my understanding that a dealer scan tool can make slight adjustments to correct those errors. I don't think that's the case for EVIC errors but really don't know.

If the trip odometer reads a total miles traveled that's 110 miles different that what the odometer shows you have a problem. Exactly what I don't know but I'd wonder about wheel speed sensor signals to the vehicle "brains"

Highspeed005 · **Joined:** Thu Apr 11, 2013 1:48 pm **Posts:** 13

Just a quick reply to the questions I saw when I scanned through my responses.

The jeep doesnt have a EVIC.

I understand the speedometer can be off by +-5% and that the OD can be off by about 8-10%. The issue is that the OD and trip OD aren't syncing, in fact they aren't even close.

The speedometer is pretty spot on according to my GPS as is the trip OD. Its the standard OD which shows how many miles your jeep has on it, is off by about 55 miles for every 1/2 of a tank.

The phone app requests I put my OD reading into the app. At half a tank, I had driven 251 miles according to my OD, and 196 according to my trip OD. I wouldn't have noticed the issue with the OD if the phone app didn't ask me to look at my OD to calculate my MPG. I only have used the trip OD in the past.

I have to be honest if this isn't a mechanical issue, I am not bothering to take this to the dealer to have them "fix" it.

hope this clears some things up.

papaindigo · **Posted:** Tue Apr 16, 2013 2:12 pm

Ok if I have it right:
1. your speedo and trip odometer are pretty much spot on when checked with GPS. I know how much they "can" be off but how much they are actually off varies with each vehicle and tire combination. My original setup with OEM tires was much more off than with my current tires.
2. your problem is a radical difference between the miles reported traveled by the trip odometer, which is correct, and the miles traveled based on the regular odometer. That's really weird and something I've never heard of although I'll admit my knowledge of how these instrument figures are derived is "stuck" back in the days of gear driven cables. I have no clue how the trip odometer and regular odometer get their figures but you might drop Sir Sam a PM/email and get his thoughts. As I recall he has the scan tool for the 05 and may have a decent understanding of what might be going on.

Highspeed005 · **Joined:** Thu Apr 11, 2013 1:48 pm **Posts:** 13

papaindigo wrote:

Ok if I have it right:
your problem is a radical difference between the miles reported traveled by the trip odometer, which is correct, and the miles traveled based on the regular odometer.

You got it absolutely right! I called the jeep dealership and they want me to come in so they can look at it. I am against that as I am short on funds right now.

My first course of action (COA) is going to be to reflash the jeep and see if the GDE Eco Tune had something to do with throwing off the mileage. I have an 87 mile road trip this Friday that should be able to answer that.

Other than that, I am just stumped.

papaindigo · **Posted:** Tue Apr 16, 2013 3:55 pm

I'd communicate with Sir Sam and Keith, GDE, before doing anything. I've had the EcoTune which has been upgraded to the Turbo tune and stoutdog has had the EcoTune and both of us got a modified EcoTune when GDE figured out how to make the EVIC mpg and fuel gauge readings less inaccurate. In all of those cases the regular odometer vs. trip odometere readings were in lock step.

Beyond that I cannot help you but I'd sure be curious what the solution is. Obviously a bogus signal or bogus reading of a signal is getting in there somehow but how and how to fix is well beyond my ability.

Highspeed005 · **Joined:** Thu Apr 11, 2013 1:48 pm **Posts:** 13

Rog, I appreciate the replies. I've made contact with Sam and hope hell PM me back when he gets my message. Keith I contacted about this issue but to no avail.

Im going to figure out if the Eco Tune is the issue before going back to the dealership since the dealership PooPood the eco tune idea citing that you could "scorch your piston heads by doing something like that".

flash7210 · **Posted:** Tue Apr 16, 2013 6:05 pm

All the gauges in these Jeeps seem to be wildly inaccurate.
I calculate all my mileage using only the trip ODO and it shows about 1-2% less than compared
to GPS of Google maps. Close enough for me.
I track all my mileage and MPG using fuelly.com. I just add the trip miles to whatever my last
reported mileage was and tally it that way. I rarely ever look at the vehicle ODO.

What bugs me most is the damm fuel gauge.
at 100 miles- still on F
at 200 miles- 3/4 full
at 300 miles- 1/2 full
at 500 miles- low fuel light

It is pretty consistent in that once the gauge needle goes past 1/2 its 200 mile till "low fuel light."
(I wont say empty because I've gone as far as 40 miles with the low fuel light on)
So, on a really long highway drive I might get as much as 380 miles when the needle hits 1/2 and
I can be fairly certain that at 580 miles I will be stopping for fuel.

hankdz · **Posted:** Sat Apr 20, 2013 12:25 pm

I have checked the speedometer and odometer against a measured 5 mile course numerous times. Both are high by exactly 5%. Another way to look at it is with 100,000 miles showing on the odometer the CRD has only traveled 95,000 miles. As to the speed, when the speedometer shows traveling at 70 mph, actual speed is only 66.5 mph.
Can't comment on conspiracy theory, but the above was performed with stock tires and drive train.
Philosophically, I look at it as a Godsend. By driving with the speedometer showing 70 mph in a 70 mph zone, I will likely never be cited for speeding.

naturist · **Posted:** Sat Apr 20, 2013 8:14 pm

While I put on slightly oversize tires, in that they are wider, but 70 series instead of 75s, they are supposed to be very nearly identical rolling diameter to the originals. In any case, my speedo went from being 63 mph at 60 mph per GPS, to being bang on. I did not check miles travelled before the larger tires, but have checked it since, and it seems be pretty close, if just a small amount lower, about 103 miles actually travelled per 100 miles indicated.

HOWEVER, I recently observed that an intermittant problem occurs: if I hit a small bump in the road just right, both the ABS and Brake lights come on, there is a ding, and the ODO stops recording mileage entirely. The speedo continues to operate normally. I am told that this is due to the sensor reporting unbelievable/erratic data. This sensor is located on the rear differential and I'm also told that sometimes the sensor needs replacement, and sometimes just cleaning up the connector and putting in dielectric grease before replugging it will do the job. I have not yet done that, since this occurs infrequently and it always resets next time I switch off and restart. Plus it's been a cold spring . . . .

Anyway, I routinely get 28 mpg (no EVIC here either) and have gotten as high as 34.75 mpg under ideal conditions, with a GDE ecotune.

But now you all suggest I need to do a much more careful check on my odo reading. I will do that this coming week and report back what I find on my CRD.

woodtick · **Posted:** Sat Apr 20, 2013 9:42 pm

naturist wrote:

In any case, my speedo went from being 63 mph at 60 mph per GPS, to being bang on.

Could the GPS to speedo readings with old vs new tires could the difference be worn down tread making the rolling distance per revolution shorter than the new replacements?

Odometer and Trip Odometer off by 110 miles per tank

Who is online