Valvoline DEX/MERC trans fluid

I did a filter change, flush and fill on the AW4 in my '00 XJ over the weekend using a standard NAPA filter and Valvoline DEX/MERC fluid. It seems to be shifting a little better now, but it does appear that my mileage has dropped somewhat. It's only been a few days (and maybe 100 miles driven) so I'm trying not to worry yet, but I am a bit curious.

I knew not to use synthetic fluid, but completely forgot about the certification no. ensuring it was "true" Dex-III fluid when I bought the Valvoline stuff. Anyway, the only number I can find on the bottles is "G169C2 1509" and now I seem to remember that number should start with a "D" to indicate "true" Dex-III, but I could be mistaken.

So, I was wondering who else is using this same fluid in their AW4 and how does it seem to be working?

Thanks.

If it says Dex/Merc that is what it is.

Fuel mileage is calculated and averaged using several complete gas tank fill-ups.

all the "newer" Dex fluids are backwards compatible but..... My self I will stick with Dex III for as long as I can, as its is slowly disappearing as the new stuff comes out. But just like the old "type f" fluid, Dex III will not completely disappear either so us older Cherokee guys are safe. All the new stuff has to many new chemical additives that my 89 was not built around. So for me and my piece of mind I only use Dex III.

According to my mileage/maintenance log book, I've lost about 3 mpg's since I did the trans fluid/filter, t-case fluid, spark plugs and serpentine belt (about 3000 miles ago). Highway mileage before was a solid 22, but the best I could get out of her on a 500 mile trip on flat highway last weekend was 18.9. Wasn't heavily loaded and wasn't pulling anything either. Of those 4 things, the only one I think could have that impact would the be the trans fluid.

So, I'm going to try and find some different fluid with the certification number and flush the system again. Anyone know of a DexIII fluid out there that currently has the certification?

Thanks.

Maybe you had a headwind? Not sure, that could change it. Also interested in seeing what happens when you change out the fluid.

that reminds me... need to find an airspeed indicator on ebay or something, wonder if I can find a way to rig it into my OHC as a fake temp sensor with a few digital potentiometers or something.

When's the last time the O2 sensor was changed? In my experience, this item is one of the most important contributors to MPG, but the most overlooked. I like to think of it as the 'Magic Bullet' as it is what controls the mixture, fine tuning it. And lately, the prices aren't so bad. If you can't remember, or don't know, give it a shot.

Dexron III is no longer licensed by GM for manufacture and hasn't been for several years. The stuff you are buying now that is marked Dex III is going to be a "compatible" formula containing whatever the vendor thinks is close enough.

Dexron VI is the fluid that is currently manufactured under license by GM. It is backwards compatible with previous versions of Dexron. I run it in my AW4 and NP242 with no issues.

I don't think your mileage drop is related to the trans fluid, just coincidental.

Here is JP Magazine three part article on XJ mileage. I found the power steering pump problem to be particularly interesting:

MPG:


http://www.jpmagazine.com/projectbuild/154_0808_building_a_fuel_efficient_jeep/index.html


http://www.jpmagazine.com/projectbuild/154_0810_building_a_fuel_efficient_jeep_part_2/index.html


http://www.jpmagazine.com/projectbu...cherokee_xj_project_mileage_master/index.html

Wanted to provide a quick update for you guys...

I did some further review of my log book and it turns out I was not getting the consistent 19/20 mpg average I thought I was on my daily commute. The average was more like mid-18s. So the drop to mid 17s I experienced was much less drastic. That being said, I still thought something was amiss because the mileage continued to drop. I was in the mid/low 16s by the end of '09.

So, on New Year's day, I went ahead and changed the fluid again. Did a full flush/fill with Castrol Dex/Merc Multivehicle ATF this time. First tank, 18.3 mpg. The second was a fluke at 15.9 (not sure what happened there). Third was 18.4 and fourth was 18.2. Considering that I put in regular dino 10W-30 the last time and am running winter blend gasoline in cold temps, I think things are back where they're supposed to be.

She's getting ready to turn 160K and as far as I know the O2 sensor is original. So, that is on my list to be replaced here shortly.

What is the service interval on the late model XJs o2 sensor?

On earlier models it was 60k.

That is one sensor that likes to turn to crap without throwing codes until things are really bad, and then it is usually another sensor that triggers the code.

joe_peters said:

I don't think your mileage drop is related to the trans fluid, just coincidental.

Click to expand...

Completely agree. Continue to look elsewhere.

How fresh are your spark plugs? As Joe mentioned, the oxygen sensors can get "lazy" and contribute to a drop in mileage without tripping a check engine light / code.

Like I said, O2 sensor is next on my list as I have also read that they can start to go bad and impact mileage w/out throwing a code.

So, maybe it's not the complete "fix", but I did notice an immediate increase in mileage just by changing to a different Dex III fluid...

Plugs were new about 9,000 miles ago.

The new engine oils are low on additives, and unless you are adding a can of GM EOS at every oil change, you prolly have a flat cam lobe on one of the 12 contenders... Take the pan off, and look up at the cam... I'll bet one of those lobes is very worn.

I don't really know much about the 00 XJ but one thing I've noticed in earlier models is disconnecting the battery, then reconnecting and having the computer relearn can be like throwing the dice.
I've had some pretty wild mileage swings, just because I disconnected the battery.
I've experimented some, seems letting it idle after reconnecting the battery is the worst.

XJ O2 sensors have a service life of approximately 100-150,000 miles. As the miles add up they are slower to respond and can effect your mpg's A 30-30% drop in mpg's strongly suggests O2 issues. Cat converter have a service life of approximately 150,000 miles. Like windshield wipers or mufflers, the O2 sensors and Cat converter are routine service items. When they wear out, or no longer function correctly, they are replaced.

It is highly unlikely that your choice of transmission fluid has an effect on your mpg's and having more extensive mpg records from before and after the fluid change for any comparison would be recommended.

The Dex-III/Mercon formula is no big secret, so any fluids you buy that are labeled meets or exceeds the specifications for Dexron-III/Mercon, probably does.

ZDDP, or lack of it in modern motor oils, does not have an effect on gas mpg's and since the 4.0L is a low reving, non-high performance engine, reduced levels of ZDDP in the oils probably has no effect on the service life of the 4.0L engine. I fully expect another 150,000 miles from my 4.0L using current spec motor oils.