Driving habits are the main factor. I haven't noticed much if any difference in mileage since I bought my Ram and I'm almost to 6K miles.

 

In my case is not driving habits, but driving conditions. There is always traffic and unfortunately I can control the wind directions when I drive. I aint no Bruce Almighty. I broke my engine in a while back and its no better, not even with the original ST tires was better. Its funny how car manufacturers abused the incorrect information the EPA was giving them. All their commercials brag about their high MPG on hwy numbers. GM is one of them, now that stupid Jeep with the bobbling heads.

 

my mds kicks in over 65mph....that is all i do is interstate driving and since i got my exhaust installed i can hear every time it (the MDS) turns on and off. It does not turn on as often for various reasons like wind, road incline, and obviously traffic. When the road is nice and flat i can cruise at 75 and have the mds working consistently. I avg about 19mpg on the highway at about 75mph. 2006 qc ram 1500

 

I pray to the gas god's to bless my hemi with 13mpg. I've never seen 18 even on a 80 mile interstate run. im running 3.92 as well

 

I got 17.5 today!!! It was hilly stretch of road in Mid Michigan... 55mph for 30 miles.

 

My MPG kept improving past 10,000 miles.There are no flat roads in northern Jersey. I have found my winter mileage to be somewhat lower in the winter due to the gas formulation and the choke. Notice how long it takes to get to the "normal" operating temp?"

With almost 32,000 miles I get about 13 city driving, average high 15s on the highway without MDSdepending on speed. Taking the state highway with traffic lights produces better mpg than the interstate. I have found I will be in the area of 20 mpg at 50, 17+ at 65 and lucky to get 15 at 75, but speed feels good to this old man. The feds calculate the MPG at something like 50 MPH. There is talk that the testing is being revised and will decrease the sticker rating by 10% by using more realistic driving speeds. GM, FMC, and DC are fighting the revisions

I have nogas saving or performance accessories, but have found two modications that have increased mileage
(1) Changing to Mobil 1 was worth maybe 1/2 mpg, switching to 5w20 over 5w30 quieted (not eliminated ) the hemi tick.
(2) Increasing the psi in the tires is good for at least a full mpg. The ride is not bad on the regular cab running 44 in the front and 40 in the rear on the 265/70x17. The 140 inch wheel trucks will ride even better.

The above mpg calculations of actual, not the computor. My computor is high by approximately .5 to .8 mpg.

 

So... Let's straighten this out.

Does MDS turn on after 65mph?
If you say it doesn't show me proof.
If you say it does show me proof.

I will be calling a few people in Corporate when I get a chance.

I cannot think of a single freeway near me where the speed limit is below 70mph... you try doing 65mph on I75 without people getting pissed

 

The MDS will come on if the engine is less than about 40% loaded, because when it drops to 4 cylinder operation those remaining cylinders will become about 80% loaded.

Anything 'natural' that lowers engine load
(wind at back, slight downhill, hot air temperature, concrete pavement) will allow the MDS to stay on to a higher MPH.

You can also make modifications to lower load,
such as better aero
(lowering, tonneau, airtabs, deeper front airdam or blocking off part of radiator opening)
or lower tire rolling resistance
(higher air pressure, worn down tread depth, rib tread design, more SiC in rubber instead of carbon black)
will also allow the MDS to stay on at higher speeds.

Here's the official DCx press release:
----
Maximizing MPG with MDS; Tips from the Chrysler Group on Getting the Most Fuel Savings with Its Multi-Displacement System * Chrysler Group MDS improves fuel economy up to 20 percent * Standard equipment on almost all HEMI 5.7L engines AUBURN HILLS, Mich., April 20 -- Just a few simple tips can help owners of Chrysler Group engines with Multi-Displacement System (MDS) get the most fuel mileage possible from their 5.7L HEMI(R) V8 engine. The customer does not need to drive in a certain way to realize a fuel economy improvement with MDS, but these driving habits can maximize their fuel savings with this technology. * Keeping speeds to 65 mph or below -- MDS uses four cylinder mode most at these speeds * Use cruise control -- this helps maintain a steady speed, generally allowing the HEMI to run on four cylinders for longer periods * Accelerate more gradually -- the HEMI will provide V8 power whenever it is requested by the driver * Use a steady throttle whenever possible -- this maximizes four cylinder mode The Chrysler Group MDS is standard equipment with the 5.7L HEMI on seven vehicles: the Chrysler 300C, Dodge Charger R/T, Durango, Magnum R/T, Ram 1500 and Jeep Grand Cherokee and Commander. With the addition of MDS to HEMI-equipped Dodge Durango and Ram, MDS-equipped vehicles through the end of the 2007 model year will save more than 60 million gallons of fuel each year. The Chrysler Group MDS seamlessly alternates between smooth, high-fuel- economy four-cylinder mode when less power is needed, and V-8 mode when more power from the 5.7L HEMI engine is in demand. This optimizes fuel economy when V-8 power is not required, without sacrificing vehicle performance or capability. Chrysler Group was the first to offer modern, large-volume vehicles in North America with cylinder deactivation -- the HEMI-powered 2005 Chrysler 300C and Dodge Magnum R/T went on sale in the of spring 2004 with the Chrysler Group Multi-Displacement System, or MDS. Chrysler Group was also the first to offer cylinder deactivation in an SUV with the introduction of MDS in the 2005 HEMI-powered Jeep(R) Grand Cherokee. Chrysler Group is the first to offer MDS in a pickup truck -- the 2006 Dodge Ram 1500. MDS is a fuel-saving technology that is here today -- customers get the power and capability of the HEMI V-8 that they desire with the fuel economy of a less powerful engine. [/align]

 

You said I can’t drive slower, says WHO? You can drive slower than 70 MPH if you want to or want better mpg. Who cares if the others get pissed if you drive 65 MPH in a 70 MPH zone, you’re the one who has to pay for the gas not them. BTW most states have a minimum speed of around 40 MPH, so as long as you stay above the minimum you should not get a ticket for driving 65 MPH. It all comes down to this, everybody needs to decide if they want to drive 70 MPH or faster or get better MPG that will save them $$$ by buying less gas. BTW, if you want super MPG then buy a small car to drive and not a pickup.

 

If I am reading this correctly, it sounds more like 65mph is the average speed where your MDS will cut off not the highest speed when it will cut off. When you are driving going 70mph are you driving up hills? In traffic? And are you using your cruise control? If you are not using your cruise control I would suggest using it. Also go 65mph and hit the cruise and wait for the mds to kick in and then by using the cruise control slowly increase your speed untill it kicks out of it so you know how fast you can go til it kicks out. I'd also try adding a few mods to help the truck breath easier and thus not work as hard whch should help with your mpg as well as helping you mds mode.

On a side note dont be one of those people who drive under the speed limit unless you are by yourself on the road. People now days get very veryimpatientwhen others do this and it can escalade into road rage in some cases. We've all been behind someone like that at one point or another and when that person is going lets say 60 in a 65 the cars about 5-6 back are going around 50 and slowly slows down everyone behind them. So if going 70 is really that big of a deal try a different roadwhere you can go 45 or so.