Turning off MDS kills my gas mileage..

[adrianp89]

I think there is some placebo going on here. No way with it off you guys are getting better gas mileage. This is no where near my field of specialty... but unless someone can explain in detail how it is possible then I'm not buying it.

 

[SlowRoller]

If you're talking to me. I run the 87 canned tune.

Nope. See post 10

 

[SlowRoller]

I think there is some placebo going on here. .

Most likely a 'before/after' effect, with a whole lot more going on in between than just switching MDS off.

My best so far? 24.8 average after a 200 mile loop. (Houston/Galveston/Freeport/back to Houston) Lotsa 70 mph, with a little 45 - 60 involved.

Bone stock Quad w/3.21's. Not too shabby for a 5.7. (or is it really just a 2.85 in MDS mode? LOL!!!)

 

[Casper]

So I've been running with it out since I bought the truck two years ago.

Read all the threads about turning it off and how great it is.
Turn it of and really didn't notice much of a difference. Exhaust sounded the same and acceleration might have lagged a little less.

Ran it for two fill ups and got barley 12mpg. With it on I was get mid 14s.

So just my 2 cents..lol

Let's face it, Chrysler wouldn't spend the money on MDS if it didn't help them with MPG (or smog or something else). There is very little altruism in manufacturing.

Since they do spend the money to put MDS on every HEMI, there must be a reason--like shutting down four cylinders uses less fuel.

Of course MDS is annoying because when combined with an overdrive transmission, it means you have to mash the skinny petal to get all 8 cylinders back, and then get a downshift for acceleration. Four cylinders lugging in overdrive is why you get the exhaust drone as well.
One way to reduce the MDS lag is to anticipate the need for a goose of speed and start on the skinny pedal early; its not nearly as annoying that way as all you're waiting on is the downshift.

 

[KahneFan]

...are resetting the evic once they are up to speed. Then they quote the evic reading...

I have no idea what you're speaking of here, but check out my MPG with my PMS turned on!

 

[BlownGP]

I have no idea what you're speaking of here, but check out my MPG with my PMS turned on!

I got that in my old car going down a bridge. lol

 

[ramrunner56]

I turned off mds a month ago. Driving in town I had lost some mpg. I thought the guys that said they gained mpg with it off I thought were nuts. Then I saw the gains

I did my drive from oregon to north dakota and gained 3 mpg for the drive. I had made the drive 4 or 5 times and the best I could do was 18.5 mpg on the evic. This last time with it off ot was 21.5 or maybe even a little better. I'm still getting 18-19 mpg to and from work out here but it's a straight shot no traffic lights or stop signs

How do people get that good of mileage on the highway? I drove from Nebraska to branson, MO at about an average of 80 and I only got 14.5mpg. That's the best mileage I've gotten out of this truck.

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[bassheadhemi]

How do people get that good of mileage on the highway? I drove from Nebraska to branson, MO at about an average of 80 and I only got 14.5mpg. That's the best mileage I've gotten out of this truck.

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Found out that going over 70 hurt the fuel economy real bad, the issue is probably the aerodynamics of the truck since the RPM difference is minimal

I found that 50-55 is the sweet spot for me, on a flat road with no wind I can go over 30mpg.

At low speed (traffic) or frequent stop MDS actually is worse according to the EVIC. If I disable it, it take less throttle to move (while already in movement) and the live mpg bar move a lot less too.

 

[ramrunner56]

I had a feeling that was part of it. When I'm on the highway I'm usually at 75+. In the city I speed at 55 but most of my driving is busy traffic so my mileage is absolute crap, 10-11.5

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[RR7_905RAM]

I'm with Davidram lol

You can tell me to go RTFM but anyone want to give a quick lesson on where and how to turn on/off?

 

[adrianp89]

I had a feeling that was part of it. When I'm on the highway I'm usually at 75+. In the city I speed at 55 but most of my driving is busy traffic so my mileage is absolute crap, 10-11.5

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I can average about 20 at 70-75. I have the 8 speed and 3.21s though.

 

[ramrunner56]

I can average about 20 at 70-75. I have the 8 speed and 3.21s though.

I have the 5 speed with 3.92s, but does my outdated tranny and low gears make that big of a difference?

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[bassheadhemi]

I'm with Davidram lol

You can tell me to go RTFM but anyone want to give a quick lesson on where and how to turn on/off?

Just put the transmission in manual mode (8th gear), it will shift the same but MDS will not kick in.

If you have a tuner you can disable it permanently

 

[Casper]

I have no idea what you're speaking of here, but check out my MPG with my PMS turned on!

I could do that too if I only coasted down hill

 

[Rzrman328]

How do people get that good of mileage on the highway? I drove from Nebraska to branson, MO at about an average of 80 and I only got 14.5mpg. That's the best mileage I've gotten out of this truck.

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Anything over like 65 and mpg will suffer.....at least that's what I've always thought.

The best I ever got was 19-20mpg. Obviously before being lifted.

 

[Kotta390]

I have found out that turning off MDS will hurt the fuel mileage slightly on the highway. I cruise 70mph for 35 miles everyday to and from work. While I haven't done a tank to tank comparison, I can tell that my EVIC will show roughly ~.5mpg drop in fuel mileage. If I am in the city, I turn it off, because the MDS lugs the motor quite often when off and on the gas.


IF you turn off MDS, I have also noticed on the 8 speeds at least, that the shift schedule for downshifting is a bit more aggressive. when coasting, it will make no difference that I can tell. BUT, if you are on the brakes, it's almost like the trans downshifts the exact same way as you are in tow/haul mode. Kinda weird, but whatever. I have a very basic truck and it's a RCSB, if turning off my MDS is affecting my fuel mileage, I KNOW it has to be affecting the QC and CC gas mileage as well on the highway. As far as city, I can't tell a difference, other than that I don't get the MDS drone.

 

[KahneFan]

Something also to throw out there is, how many of us do/don't have the active grill shutters and what difference is that making in our mileage.

Pulled my grill off the other day and got a good shot of mine while I had it off.

 

[SilverStreak88]

I turned mine off with my tuner and it gets better mileage and performs better. Now I've been running with it off since early 2010 and when I get industrious I'll change the tune and turn it back on. I don't know if it not cycling for so long made it where it won't give me good MPG anymore, but I can get around 12.5-13 easy and when I turned it back on I would be getting high single digits.

 

[Kotta390]

I turned mine off with my tuner and it gets better mileage and performs better. Now I've been running with it off since early 2010 and when I get industrious I'll change the tune and turn it back on. I don't know if it not cycling for so long made it where it won't give me good MPG anymore, but I can get around 12.5-13 easy and when I turned it back on I would be getting high single digits.

Idk about your 3rd gen Hemi's MDS system but the 4th Gens are much better. I also turned mine off in my 2006 and it didn't net me any better fuel mileage but it sure as hell didn't hurt it. Plus it was nice to get the MDS drone tuned out.

 

[Rzrman328]

Something also to throw out there is, how many of us do/don't have the active grill shutters and what difference is that making in our mileage.

Pulled my grill off the other day and got a good shot of mine while I had it off.

What exactly do these shutters do?