Trip Computer MPG Accuracy?

[CMusgrove]

This is a rather surprising thread to me as my overhead has always shown 1 to 2. 5 mpg lower than hand-claculated. Very pleased with truck and this past weekend on a 400 mile round trip got hand calculated 21. 7. 80% freeway. Even though speed limit was 75, tried to hold it at 67-68 (1,850 rpm).

 

[rattlbox]

my overhead is usually . 5 or 1. 5 mpg lower then when hand calculated

 

[RBollengier]

I tried finding that tsb and couldn't, can you point me in the right direction?

 

[BHolm]

On my '06 I have caught it on both sides, a little low and a little high compared to hand calc. What I can't figure out is how you guys figure a 10% deviation is such a bad deal. I actually think that is pretty dang good. Considering fuel variations I don't think they can really get it a whole lot closer.



I once had to rescue my buddy on the side of the road with his GMC. The miles to empty on his truck said 90 miles, the truck ran out of gas 10 miles from his house :-laf I just use the readings for entertainment, I doubt they were even intended to be much more than that.

 

[John Boyce]

My computer is pretty close for around town driving, but typically reads around 2 mpg low for highway driving. Stock truck. I have averaged 17 mpg (hand calculated) for my first 9,000 miles.

 

[Wal_mart]

Tsb 08-020-06

Try this

http://dodgeram.info/tsb/2006/08-020-06.htm

 

[mwhals]

I showed 18. 2 mpg and calculated 16. 3 mpg.



I showed 17. 2 mpg and calculated 16. 2 mpg.



Two similar actual mpg calculations, but two totally different readings from the computer.



Mark H

 

[BHolm]

How can anyone reasonably expect these things to be right on your hand calculations? How does the computer account for tire wear? How can you be so set on a few tanks hand calculated? The margin of error for just a few refuelings is way more than what you are complaining about in the trip computer.



Two totally different readings?????They are 1 mpg apart. I am honestly finding it hard to believe there are two pages worth of this thread.

 

[Bernie]

Yes, I do think it should be accurate

For the following reasons:



-From what I can tell in the TSB discussed above, it use to be more accurate (actually starting at 0 from the reset point). Now it starts from whatever the last milage was at reset. That will give increased reading that is not accurate. The way Dodge used to do it (starting at 0 with reset) is more accurate.



-Every other vehicle I have had with a MPG display was very accurate (off at most by . 5 MPG, usually off less than . 3 MPG). If other manufactures can make an accurate display, why can't Dodge? (and all of those vehicles cost a lot less than my truck)



-Someone earlier mentioned fuel quality affecting the display. It won't, because all that is needed to figure MPG is how much fuel moves through the system for a given distance traveled. If the fuel is poor, more will need to be moved through the system to travel the same distance, and that will be reflected in a lower MPG.



-The amount of times that the axle completely turns is how the truck calculated distance traveled. Yes, a worn tire may moves is slightly less distance per revolution of the axle. Yes this may on a very very very small scale affect the actual MPG (but, that is out of our margin of error for the following reasons). This will still not explain the difference between displayed and hand calculated MPG, because both the truck and me are using the same distance (odometer) that will be equally affected by any tire wear issue. Again, all we care about is fuel used and distance traveled.



-I travel a lot of miles, and I check each tank. I have hand calculated every tank of the last 16k miles (new truck, had it about 3 months), and the actual MPG is consistently about 2 less than the indicated MPG.



-I expect accuracy from a truck with a $44k sticker price.

 

[RBollengier]

The only other thing more irritating than this trip computer is the cup holder, if this is worth two pages the cupholder is three at least. I guess if this is all I can complain about Dodge has done a good job.

 

[BHolm]

The only other thing more irritating than this trip computer is the cup holder, if this is worth two pages the cupholder is three at least. I guess if this is all I can complain about Dodge has done a good job.

Now there is a sentiment I can get ahold of If this is as bad as it gets, it makes me even happier that I own Dodge trucks.



To expect more from a $44k truck is great. Mine last one was $56k, and for that I would like to be able to expect a lot more on many fronts. How about a quality stereo system, the best stock one is garbage, other manufacturers do better. I want better seats and leather that isn't paper thin, others do that better too. I could think of a whole list.



If a 10% error on the trip computer is what burns you... . then best of luck. You let DC know owners are REALLY unhappy about it, maybe they will fix it, but don't hold your breath.

 

[HNelson]

My 06 reads 1. 5-2. 5 mpg high all the time. I think I had one tank within 1mpg, it was towing. But I've had other towing tanks off 2. 5 mpg.



My 05 was always within 1 mpg. They probably found a way to cheapen it by taking out a sensor on the 06's and just substitue a guess in place of the measurement. If I ever take the truck to the dealer I'll complain about it.

 

[TMoe]

trip computer

My 01 was way more accurate than my 06 so far. I could actually do better than the computer with Edge EZ. What's disappointing is the test drive said 20, makes you feel good, and the actual is 17. They also removed the instantaneous readout which is all I used on the 01. I feel it is all about lowered mpg and Dodge knows it. I don't drive that much so it doesn't make much difference to me. I feel for those whose income is affected by the mpg. In those cases this is a real load of crap. There is no excuse for this not being very close with knowing pulse width on injectors and distance, as others have mentioned. For me personally truck is a big improvement over 2nd Gen in many ways but, for now, mpg doesn't look as good. Every time I drive it I can't believe the quietness (love it), brakes, headlights, steering and did I mention how much I like the steering. Dodge makes a real nice diesel truck now. I only hope I can say that after 100,000 miles, enjoy.

 

[JDHenning]

Computer vs. hand

My 2006 has always read lower than hand calculated. As little as 2/10ths and as high as 1. 2 mpg. I wonder how much of the deviation comes at fill up. Ambient temperature, quality of fuel, patience of the person nursing the tank full etc. My 2001 was almost always dead on even with the Edge Comp. I've noticed when I fuel at QT sometimes the fuel is more prone to foaming which makes it harder to nurse the tank full. A half a gallon could throw things a little bit. Also when I use the 1 1/4 nozzle its harder to top it off. Just my experience. Love the truck.

 

[RCMerrill]

06 2500 My millage will go from 13 to17 mpg. if i keep resetting it every 1/2 mile i can dial a milage. HaHa!

 

[JVolpe]

Let me see, mine started out about . 9 mpg on the low side. I have hand calculated mileage on every tank since new. After the TSB to make it more accurate it went to 1. 3 mpg to high. Every performance box/downloader has changed the accuracy, which is to be expected. Now mine is 5. 4 mpg too high with my current triple stack. Good thing is my mileage has improved a lot since new. I now average 14+ all city and 19-20 highway at 75mph. It would be nice however if the 24. 9 mpg computer readout was the real thing .

 

[rweis]

We have a distance measurer (rev's) in the diff case assumming you have stock tires or can reprogram. Does the VP measure fuel quanity used, or is that where the DC guess factor is.



Bob Weis

 

[J&LRam]

my '03 shows 19. 5 to 20. 3 but pencil figures 21. 8 to 22. 5 on my 110 mile a day commute. I very seldom reset. Towing my 11200 lb 5er the overhead show less mpgs than the pencil.

JIM

 

[DZLROKET]

Wait! how about the seat "clunking" on exceleration? AND the Lumbar support "unwinding" in a half hour or so if driving?????

 

[cbmkr]

Mine always reads low , the dic is only a mileage indication, to really figure it do a hand calculate . Then check your overhead, take your trip mileage and your DTE miles add those up and divide by 35 tank capacity. (the computer should do this for you but they are not setup that way anymore),I just ran four trips 70 to 72 mph highway,450 miles approx one way and showed 16. 8 on DIC hand calc was 20. 5 with tailwind , 19. 6 ,19. 4 and 18. 3 30 mph crosswind on the last run but the dic showed 14. 7 on that one. I really only watch it once in a while to try and notice a problem with fuel ect.