Dumb question RE: MDS

[BigBadMagnum99]

I feel pretty dumb, but I thought I would ask! With all the runs back and forth from Home to Vancouver Childeren's hospital with our son (3500 km worth) in less than 2 months our MPG has dropped somewhat since we took delivery of our 06 Magnum RT AWD.

Our first 1500 km of driving we avg. about 15 to 16 mpg city driving and 22 to 24 mpg highway. We have just alittle over 5000 km on the motor and our fuel mileage has dropped to 13 to 14 mpg city and 19 to 21 mpg highway. We have not changed our driving habits since we took it off the lot.

I maybe think it has to do with the colder weather, and possibly the winter fuel blend and a small possiblity of running true winter tires (softer compound) that may have been affecting our gas mileage slightly. Also, I feel that the motor still has to break-in. I figure around that 20,000 km the Hemi should be broken in and getting better mileage than new.

However, after our first oil change at 5000 km I was bored and started reading our owners manual and somewhere it stated that if you have the battery disconnected you should take the car in for a flash or check to ensure the MDS is functioning correctly. As we drove home I remembered we did have the battery disconnected about that 2000 km range for a re-install of a all-in-one DVD system for our kids.

Now here is my dumb question:

Should I get our Magnum RT flashed for MDS function because of the battery disconnection for the DVD installation?

Would this be the cause of the MPG going down slightly from new?

Any thoughts would help.

Thanks,

BB Magnum

[COLORADOMAGNUM]

I know here in Colorado we use a "winter blend" gasoline from mid-November to mid-March to reduce air pollution. This causes a 2-3 MPG reduction in our cars. My Magnum, and my wife's '04 Chrysler Pacifica are both affected. Might be the same problem you're having.

[wheelife]

I am not sure about the M.D.S. but I have snow tires and I to noticed a similar drop in fuel economy also letting it warm up when really cold also seems to squew things and I also have the steel rims which weigh more than the alloys.

[bigjim]

I have the same thing going on, I just left it to the winter tires as it went up right away last spring when I changed back to summer skins.

[Smoove06CSRT]

do the wot recal.. or whatever it is called... worked for me. look in the knowledge base.

[Todd RT]

Actually the 'throttle calibration' has been proven with a Starscan to be basically 'urban legend'.

I've personally had luck with the 'MDS Calibration', here's a quote from the service manual:

http://www.lxforums.com/board/showpost.php?p=181677&postcount=13

[fnkychkn]

http://www.lxforums.com/board/showpost.php?p=181677&postcount=13
this link is from an old TSB. the TSB has since been updated and the MDS relearn portion has been removed because they(DCX) say it is not required and that it will relearn on it's own.

[345hemi]

I too have an 06 AWD R/T now with 11,000km ( 6500 miles) - the best i have ever seen is 12l/100km with equates to 19.6 MP US Gal and about 23.6 MP imperial Gal.

I am in the Vancouver area of BC so we should have similar gas except I am at sea level. i did a business trip 2 weeks ago - a 400km round trip in one day and average 11.8l.100km using cruise control as much as possible (set on 120km/h ( ~75MPH) It was raining heavily the whole trip which may have caused some degradation in economy. My usual commute nets me about 16l/100km or 14.6 to the US Gal or 17.6 to the Imperial Gal/

Unfortunately it appears that feeling 340 ponies through all 4 wheels comes in at the same figures you are seeing.

[Smoove06CSRT]

Actually the 'throttle calibration' has been proven with a Starscan to be basically 'urban legend'.

I've personally had luck with the 'MDS Calibration', here's a quote from the service manual:

http://www.lxforums.com/board/showpost.php?p=181677&postcount=13

yep, That is what I meant... I did that and instantly got back 3 mpg...

[BigBadMagnum99]

Thank for all the tips guys. I tried the old TSB for battery disconnection when I got home from work and....it seems to have worked as I took it for a good 50 km city drive and I am seeing the numbers I started with out when we took it from the dealers lot.

With the short city drive a few WOT's we are back at 15.7 US mpg all city driving. I will give it a good highway run as we have to take our son down to Vernon Jubilee Hospital for some tests and a check-up! I will post what we get highway mileage to see if this TSB really worked!

Thanks again for everyone's output!

[Zog]

Sounds like the oil change was when things went south...did they put the right oil in it?

Anything other than 5-20 may cause significant fuel mileage decrease.

[BigBadMagnum99]

Sounds like the oil change was when things went south...did they put the right oil in it?

Anything other than 5-20 may cause significant fuel mileage decrease.

I thought of that too Zog...but the decrease in MPG happened 3500 km before my first ever oil change for our Magnum (Thanks for the heads up!)

I ensured my dealer (5 star) on the Magnum's first oil change that the MDS hemi's only takes 5W20, not twice but three times. Also, informed them that if they placed the wrong oil I would be back very soon and they would be changing my oil again to get the correct oil in the Hemi.

During the oil change by my dealer they showed me what oil the mechanic placed in the car and I ensured my iwork order and my invoice had 5w20.

I figured out that the reason for the MPG drop was because of the battery disconnection when they had to re-install our DVD player. The knowledge base for battery disconnection in regards to MDS re-learn steps worked like a charm as the Magnum is back to the MPG we initially had when we first drove it off the lot (all US gallons) 15 to 16 MPG City and will be testing the highway mileage today as we go to Vernon with our son and I am thinking it should be around 23 MPG.

Thanks again for the suggestion Zog!

[Zog]

You're welcome!

[kinsco276]

You guys have to forgive my ignorance, but what is WOT? And give me the instructions for re-setting the MDS again. I read the link, but not sure I follow it. Thanks,

Kevin

[PaulFix]

WOT= wide open throttle.

With the car warmed up, stop at the side of the road, autostick down to 1, wot to 4500rpm ( takes about 1-2 seconds) foot off gas allow car to coast down to 20mph, pull over, turn off engine.