Mucho thanks cv2003 .... you have given me pause for thought.

First I am with you on questioning why no other indicators of "something" not right causing mileage. I pay close attention and meticulously maintain my vehicle - it runs like a clock.

As to my mileage numbers: The van is only driven Sept - March here in northwest (stored for other 6 mo of year). The 18 mpg city is interpolated and comes from the only "certain" data I have from last year which is 21 mpg hwy. (Note: I drive a 3.8L GC as taxi in Alabama in summer and it routinely gets 17-19 combo city/hwy and 21.5 hwy). The 13.7 comes from several accurate mileage calcs I have done this year. This number just seems very low - am I too optimistic here?

Thanks for the questions ... I'll try to answer:

1) and 2) answered above. Did not know about the winter gas factor - this could account for some of the numbers. I cannot say with certainty how rapid the change has been.

3) No to all. Driving routines and habits same.

4) Calculate mileage from "top off" baseline then fuel consumed / mileage driven.

I agree good idea to now step back and get some more hard numbers.... especially a couple of hwy mileage tests (since this is prob best comparison I have with last year). But I have to say if it turns out there are no malfunctions and 13.7 is "the" city mileage I can get it will be a big disappointment. Again appreciate the time to answer cv2003.

I will keep this thread updated as the saga unfolds... maybe can help others.

 

Thanks for your honest and accurate follow-up, which fills in the blanks, and goes a long way to explaining what you reported previously.

From what you wrote in your reply, it's apparent that 18 mpg city never actually physically happened for this van. I understand you thinking it's logical to derive that number based on the Alabama van, however it's really apples to oranges. The travelling you do in those 2 cities has to be different, probably in a number of ways. The number and duration of stops and slow downs is different, and how much time is spent at higher speeds varies as well. There's no possible way to compare them - simply just too many variables. And with Alabama never getting Winter blended gas, that's going to make a 1 or 2 mpg difference as well (assuming that the Northwest does get Winter blends).

I understand you being disappointed with 13.7 city, but that number is definitely not 'abnormal' - many other folks report similar numbers. And the only way to improve what your getting is to make changes to your commute. Perhaps something like driving more miles, but at higher speeds with less stopping.

Bottom line: this van's 21.5 highway is completely typical, and IMO your van has no 'problem' causing 13.7 city mpg. Unfortunately it is what it is.

 

Yes, it makes a bit more sense now that I have that perspective cv2003. Agree with Cougar41 more hwy numbers are needed now. I will hold off on other actions until then - unfortunately with my situation its hard to get straight "freeway" time so it may take a while. I will post results to this thread.

Really, really appreciate everyone's participation. Great tool this "internet thing".... when knowledge/experience can be shared so readily. Stay tuned for the rest of the story.

 

For everyone here is some add'l info on upstream O2 sensor for 05 3.3L (also posted on the other Dodge Talk forum):

If I eventually change out upstream O2 sensor it will be NTK (part # NTK23566). If so, kind of a hassle because there is a TSB out which says must do a PCM re-flash to make sure the system is calibrated with PCM and performs properly. Apparently it has to do with a mid-year change made by Dodge.

So it ultimately means having to go to the dealer... for PCM flash. Hopefully it is covered by Dodge as "mandatory" maintenance.

More on the NTK TSB which says mandatory to do re-flash when replacing upstream O2 sensor:

According to the NTKO2-TSB-0414-EN after mid year change (Jul 2004) Grand Caravan has XZZ option code and uses sensor OE# 56029085AA only. It also required PCM software change (because O2 sensor specs went from 2-4 ohm to 7-10 ohm).

Apparently there are discrepancies in some vehicles on the road, i.e. software and sensor do not match. So only way to be sure is to put the XZZ option sensor in and flash the PCM with "known good" software.

I sincerely hope I do not have a mismatch in my van causing the poor mileage. Have to evaluate my hwy mileage results before looking at this or anything else though.

Stay tuned.

 

One of our vans also happens to be an '05, and I've become very well acquainted with the different parts (EGR changed along with the O2), as a result of the mid-year build change (i.e. the XZZ option). I'll say for certain this is the first time I've read anything about a mandatory re-flash being required when changing these parts.

Every prior piece of information I've seen on this says to simply install the part that corresponds to your van's build date. Most of the parts stores specify 2 EGR and O2 sensors for the '05 vans, and describe them as 'with' and 'without' the XZZ option.

The only thing I can think of relative to this reflash would be if someone wanted to install the XZZ parts into an non-XZZ (early build) van. But that would imply that both the O2 sensor and the EGR valve would need to be changed to the XZZ version.

I replaced the EGR on our XZZ '05 last year, with no issues whatsoever as a result of not reflashing the PCM. If you do eventually install an O2 sensor (or an EGR valve), I'd recommend just using the part number that corresponds to your build date, and skip the reflash.

 

Yes that makes perfect sense cv2003. Here is link to the TSB http://www.ngkplugpro.ca/content/con...nsPacifica.pdf

It seemed a bit confusing when I first read it.