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I'm looking to buy a Challenger in the next year. As i'm in the UK and fuel is Very expensive economy is a consideration for me.
So,is the MDS on the 5.7R/T only or is it on the 392 as well?
Am I right in thinking that MDS is on the A8 but not on the M6?
Finally does the MDS make that much difference at cruising speeds?
Thank You gentlemen
 

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Any automatic transmission car will have a Hemi with MDS. The manual transmission Hemi cars will not have it.

Does it make that much difference? Eh, not enough of one to keep it enabled on my own car.

I dislike the sound of the engine and exhaust when it kicks in, plus I dislike its operation in general. So I disabled mine. I’m probably losing 2-3 MPG on the highway, max. Less than that for city driving.

It won’t be a night and day difference in MPGs, that’s for sure. The engine will get a little extra mileage from each gallon with MDS running, but nothing anyone would call shocking or significant IMHO.
 

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Any automatic transmission car will have a Hemi with MDS. The manual transmission Hemi cars will not have it.

Does it make that much difference? Eh, not enough of one to keep it enabled on my own car.

I dislike the sound of the engine and exhaust when it kicks in, plus I dislike its operation in general. So I disabled mine. I’m probably losing 2-3 MPG on the highway, max. Less than that for city driving.

It won’t be a night and day difference in MPGs, that’s for sure. The engine will get a little extra mileage from each gallon with MDS running, but nothing anyone would call shocking or significant IMHO.
That's most helpful Thank You Sir
 

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It may sound trite, but keeping your foot off the accelerator will make the most difference in fuel efficiency, much more than the MDS can do.

Im not saying it’s easy to be that frugal with the accelerator, but if you can apply some self control while tooling around town, you will achieve surprisingly good gas mileage.

My first week of having the Hemi, I was getting 11 MPG in city driving. Nowadays, I’m able to get 18 MPG in the city just by acting civil and driving like a sane person.

The difference on the hiway is even more. I’m able to get 25+ MPG on long trips just by setting the cruise at 75 mph and leaving the gas pedal alone.

The best I saw with MDS doing the same was 27 MPG on a cross country trip. City driving with MDS, for me anyway, was always a wash. Couldn’t hardly tell any mileage difference.

Other folks will no doubt chime in with better results on their cars, but that’s mine, for what it’s worth.
 

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I see about a 3 to 4 mpg difference at 65 mph. I wish it would only kick in above a certain speed or you could set a default drive mode instead of the default always auto. I am not going to tune it out until warranty if over.
 

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I see about a 3 to 4 mpg difference at 65 mph. I wish it would only kick in above a certain speed or you could set a default drive mode instead of the default always auto. I am not going to tune it out until warranty if over.
If you don’t want to disable it, you can still kinda control it by using AutoStick when you don’t want it enabled/engaged and going back to Auto when you do.
 

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Don't forget, the 5.7 A8 recommended octane (I am talking US octane ratings here not EU) requirement is 89 (but designed for 87 to 89 range). The 6.4 A8 recommendation is +91. So there is that to consider as well.

984135
 

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If you don’t want to disable it, you can still kinda control it by using AutoStick when you don’t want it enabled/engaged and going back to Auto when you do.
Not sure what you mean by this. I'm assuming you are saying I should move the stick into manual mode if I dont want it, and then back into auto if i do. But if i move it into manual mode, wont that require me to shift?
 

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Not sure what you mean by this. I'm assuming you are saying I should move the stick into manual mode if I dont want it, and then back into auto if i do. But if i move it into manual mode, wont that require me to shift?
Yes, in AutoStick mode -- M mode -- you will need to use the stick (or if present the +paddle) to up shift the transmission when you deem it necessary. The transmission will not allow an up shift if the vehicle speed would result in too low engine RPMs.

On the flip side, the transmission will not auto shift up at red line like it does in automatic mode.

If you do not down shift manually as the vehicle speed decreases and engine RPMs drop the transmission will down shift on its own just like it does in automatic mode.

If you find the transmission is in too high a gear for the current situation you will have to down shift manually. The auto kick down into a lower gear when the gas pedal is shoved to the carpet is also disabled in AutoStick mode.

While my Hellcat doesn't have MDS I use the AutoStick mode quite a bit. Generally I up shift at around 2K RPMs but often enough delay the shift until a higher RPM to get a chance to hear the engine at a higher RPM.

Most of the time I seldom down shift manually preferring to let the transmission handle this but once in a while just like driving a manual transmission equipped car I'll anticipate the need for a lower gear and down shift the transmission manually.
 
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