Does MDS actually save fuel?

[DavidN]

Interesting, do you think it was the tune itself or just that MDS was turned off?

Just modified stock tune. So MDS does make a slight difference (~0.5mpg) in my case.

 

[autumnwalker]

This is interesting - I'm not debating the numbers shown on the Trinity, but doubling the fuel to 1/2 the cylinders does not make sense to me - I'm wondering if there is some sort of "misreading the data" on the part of the Trinity module where it is incorrectly showing the fuel doubling in those cylinders.

0.5 MPG hardly makes it worth while from the horror stories I am hearing from local shops around here. More around the equivalent GM tech, but severe premature failure of engines with the cylinder deactivation and infrequent oil changes (i.e. people relying on the truck to tell them when to change oil vs. regular interval). When I bought the truck they all warned me about doing a regular interval (perhaps they are trying to drum up business?) oil change vs. relying on the onboard computer.

I might start playing around with "disabling" MDS via the gear selector method. From my research this is the only (non tuner) way to disable it (i.e. tow / haul does not disable it).

 

[tones2SS]

In my opinion, the MDS does save on my gas consumption. When I take off the MDS, it sucks down gas galore. lol Just like 2005 Ram Daytona used to. lol

 

[69GWC]

When you put it in tow haul mode, doesn't that automatically disable MDS? I can assume you don't want MDS when you're hauling stuff.

No it will still do its thang if its not disabled by doing the manual down shift.

 

[R.L.K.]

Another thing to consider , if you have the 7" premium cluster I've read there's a way to tell how much time the vehicle has been in tow haul/ mode . Meaning for resale value a prospected buyer may frown on so much time in tow / haul mode by assuming the vehicle has a lot more tow/haul time than actual ... If tow/haul doesn't really deactivate the MDS then the gear selector method down to (8) for the 8 speeds and (6) for the 6 speed does seem to be the better option ...or a tunner capable of disabling the MDS of course .

For me , I tow but not normally heavy approx 4k or less .

As far as my experience with MDS , I've had no issues yet ( 55k) I am not an agressive driver at all , I have the 5.7L , 65rfe xsmn , .355 gears 2014 QC 4X4 , I've never reset my mpg's on the first screen that shows total miles (3"cluster ) not the premium 7" . My evic mpg for the life of my truck is 18.5 . I do 4wd a lot I tow a boat often and use my truck for a truck more than most guys I know . Hand calculation typically yields about 1.2mpg less than evic #s for me .
I've been leveled with bills @+2.8" for nearly 40k and I'm still on stock size tires . On long trips 500+ miles I've gotten 23.4 mpgs ( evic#s ) and 22.2 hand calculated .

I hope MDS doesn't **** the bed on me [emoji16]

For my driving style and how I use my Ram I'm very happy with the gas mileage ...I was expecting much much worse . I suppose I'll get what I was expecting next summer when I install a BDS 6" lift and 35's[emoji1303][emoji1303]

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[Burla]

From my research this is the only (non tuner) way to disable it (i.e. tow / haul does not disable it).

TH disables mine.

 

[69GWC]

Must be a 8sp vs 6sp thing in the programmimg.

 

[RLJ10X]

I've requested a non MDS tune from Sean. I asked for aggressive throttle response, while I was at it. I aim to kill 2 birds with one stone.

 

[West27]

I have also done some MDS vs non MDS mpg test and I saw around 1 mpg better. This is driving too and from work where I have a good stretch of 50mph and a few stop lights. I am very shocked with what the trinity showed and will have to do some datalogging of my own and see if I get the same results.

 

[McBroom]

So to keep the mds off in my truck I’d have to go into t/h every time I start the truck??


I Love My 2018 RAM 2500HD 4x4 6.4L
Mod list: Pedal Commander, AVS Vent shades, Solo Delete kit, molar side step rails

 

[69GWC]

Yes manually shift the truck to 6th gear or 8th depending on trans everytime to keep mds off.

 

[U&A]

In the 6.4 with the 66RFE you can lock it into 6th to turn off the MDS.

 

[autumnwalker]

Did a bit of driving without MDS today - not enough to notice fuel economy, but man does the truck seem happier without MDS on. It feels more responsive and does not lug or shudder like when going from 4 to 8 cylinders.

 

[bchap05]

I've been driving with mds off by going into 8th a lot lately. I've noticed no difference in mpg. Truck seems smoother and sounds better

 

[fijicorey]

MDS works to save fuel for me sometimes, not often though. I see no difference if there's a lot of stop and go driving or hills. Basically, anything where the truck needs to be off/on the gas frequently.

I do get better mileage if the throttle input is more steady. It's not a lot though, at most 1 MPG. I wish I could buy something that serves the sole purpose of disabling MDS. I can't justify spending hundreds on a tuner just for that reason!

 

[gypsy400]

Last weekend we took a short trip (about 250 miles ea way). On the way I turned off MDS by selecting 8th gear with the steering wheel buttons.

On the way home I ran MDS the entire trip. Absolutely identical mileage.

I did the same last summer.. about 100 miles each way.. got 0.5L/100km better mileage ( might be 1 mpg) with mds on.. and never went over 60 mph.
I bet over 60mph it doesn't do any improvement.

What I don't like is the trickery they use with the valves to activate it.. eventually that will harm the engine over time.. once the warranty has expired of course.

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[Schlotzky]

One data point is hardly scientific, but using your numbers there, the 2 cylinders are using about 7% less fuel than the 4 cylinders in your picture. That represents about 1.5MPG additional in 4 over 8 cylinder mode on the highway. That's definitely enough to convince FCA execs to implement it to get closer to the ridiculous CAFE standards.

It still takes the same amount of energy to move the truck at a given speed whether you're using 8 or 4 cylinders, but by reducing it to 4 cylinders, you're able to get around some of the inefficiencies of an individual cylinder's combustion process turning that fuel into energy so the result is a small but notable increase in efficiency. The system is obviously not without it's downsides, but it's only there to appease the EPA.

 

[rideXabide]

Wait... These things have an Eco light? Ive had the truck for a year and honestly didn't know that lol.

There is a menu option somewhere to enable it.

 

[TRXHemi]

Not nexessarily T/H, but you can use the shift keys on the steering wheel to set it for 6 or 8, depending on your tranny. Then the MDS will not kick in.

 

[rideXabide]

Any potential long term issue with never allowing MDS to do it's thing? As in a few years of never running it then finally allowing it to cycle normally.

I'm not a doctor.. but my (sizable) gut makes me think there is more potential for long-term issues *with* by using MDS rather than disabling it.