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Discussion Starter #1
My truck will barely hold at 45 mph with 4:10s. I see an increase of 2-3 mpg in MDS mode, truck just won't hold it. What are everybody else's expirences?
 

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Not sure what you mean by hold it? MDS only kicks in at an even RPM... If you start to accelerate it will turn off and engage all cylinders.
 

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Discussion Starter #3
At 45 MPH, flat, open highway. 45, no accelerating, no headwind. That is about the top speed my MDS stays engaged for long stretches.
 

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Silly question... How do you know when you're running in MDS??? I have a 2013 Laramie. Is there something on the dash???
 

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Discussion Starter #5
I don't have an dash indicator but I can feel a slight shudder and a change in the tone of the exhaust. The instant mpg goes up simultaneously.
 

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The MDS on my 06 Laramie kicks in as long as I'm under 70 it seems. Just gotta put the cruise control on nad if I'm doing 70 or less it usually kicks in shorty after.
 

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My friends 06 4x4 QC Laramie will hold it at 65 on level highway with 3:92's. I took it on a road trip last summer. With the window rolled down it's very easy to hear it go in and out. If you drive above the speed you want to cruise at, example 67 mph, then slightly let off the throttle till you hear the exhaust note change to a kind of a whooshing sound, see if it won't hold it. My Dodge Magnum will hold mds at 75 mph btw on level highway. I got 22 mpg on a tank with my friend's Laramie. Sometimes I would slow slightly below 65 to keep it in mds, though.
 

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Hmmm... I've only done up to 120km/h with cruise on, and the MDS stays on. I know it's on because ECO comes up on the EVIC. But on the slightest incline, it turns off - so it can be pretty sensitive, I guess.
 

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Discussion Starter #9
The 2500 does not have an indicator apparently. Just curious as to how other trucks, especially 6.4 owners are behaving.....
 

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MDS on mine seems to hold ok from 45 to 65 on flat ground, no head wind. Any head wind or overpass incline and it jumps back to 8 cylinders. I also noticed it likes a little deceleration before it goes into MDS most of the time.
 

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A couple years ago i was returning home from either Toronto Canada or Connecticut
I had stopped by Joplin Mo. to say Hello to Stacy, (BlueJet)
i dislike Oklahoma I-44 toll roads & slow traffic because of construction that always seems to be happening there. So i took some country roads & went down through Muskogee, a beautiful drive. My MDS was on most of the time
Here is a pix, look at the temperature, speed, & mpg


 

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Discussion Starter #12
That gives me hope! I'm gonna let it break in a bit longer and let the dealership look at it. What kind of mpg are you getting on the highway? 15-16 is about my average with short stretches around 17-18. The few times mds kicks in, mpg jumps up to 20-21.
 

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Discussion Starter #13
GTyankee,

Oklahoma roads are the worst in the nation. When leaving the state or returning, I always know as soon as I cross the state line I'm getting close to home!
 

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That gives me hope! I'm gonna let it break in a bit longer and let the dealership look at it. What kind of mpg are you getting on the highway? 15-16 is about my average with short stretches around 17-18. The few times mds kicks in, mpg jumps up to 20-21.
Here are some pics of the mpg's on mostly flat ground and maybe 10 mph winds at 70 (some tailwind) and 55 (crosswind). MDS is on in these pics. I reset the mpg that morning, drove to work in traffic and the pics were taken at lunch on about a 25 mile stretch of highways with a couple of stop lights. To and from work it averages 14+ usually.







 

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Looks like the the 6.4L could get some really good hwy mileage once this winter fuel is gone. Any one of you 6.4L owners have any good towing mpg & reports to share yet? I test drove a 2500 6.4L and didn't jump on it. I know these 6.4L's are so new yet, anything you dislike after driving them a few weeks? I thought with with 4.10's, the truck would be able to hold MDS or go into MDS easier because of the gearing. Have you ever tried downshifting a gear to help hold MDS, say from 5th to 6th? Does the MDS only work in the top gear?
 

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Discussion Starter #17
An engine code showed up today, ambient air temp sensor. This should cause some mpg issues. Going to the dealership, fingers crossed.....
 

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Discussion Starter #19
It cleared itself so I'm going to let it go till the first service. The driveline seems to be loosening up more. The mpg is creeping up, as is the speed the mds is holding.......
 

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I just did a 700km round trip on the highway... I have come to the conclusion that as soon as the RPM hit 2000, MDS turns off. I had to keep my cruise control under 105km/h in order for MDS to kick in. I averaged 13.3 litres per 100km with an avg of 80km/h speed.
 
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