Will changing the oil from 5W-20 to 5W-30 damage the engine with MDS? I read on the internet that if you put in any oil heavier than 5W-20 will shut the MDS off. I just wanted to know if there is any truth to this. Thanks

I've seen this mentioned several times here, and the caution was always to stay with the 5W20...so I do. It's my understanding that using the heavier oil will affect the MDS adversely.

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'06 QC Sport, with a hole in the roof!

What effect does it have if you don't have MDS?

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'08 Ram 1500 QC 4.7 Auto in Inferno Red, Best of 22.1 avg. mpg at 60 mph so far, 8000 miles
'03 Ford Explorer Sport Trac in Redfire Metallic, 157k miles

According to the manual, the 2500/3500 (no MDS) takes 5W-30, and the 1500 (which now all have MDS) takes 5W-20.

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2008 Ram 1500 Big Horn Quad Cab 4x4
5.7L HEMI (MDS), 20" Aluminum Wheels, Tow Package, Popular Equipment Group, Power Heated Trailer Tow Mirrors, Inferno Red, Chrome Side Steps, K&N Filter, Rhino Lining, Chrome Bug Guard

Maybe this is where the theory comes from, but I cant imagine the switch in oil alone would trick the engine into shutting off MDS. I would think a setting in the computer would also have to change. In any case, I am sticking with the manual and using 5W-20.

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2008 Ram 1500 Big Horn Quad Cab 4x4
5.7L HEMI (MDS), 20" Aluminum Wheels, Tow Package, Popular Equipment Group, Power Heated Trailer Tow Mirrors, Inferno Red, Chrome Side Steps, K&N Filter, Rhino Lining, Chrome Bug Guard

My 4.7 has MDS?

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'08 Ram 1500 QC 4.7 Auto in Inferno Red, Best of 22.1 avg. mpg at 60 mph so far, 8000 miles
'03 Ford Explorer Sport Trac in Redfire Metallic, 157k miles

Use 5w-20

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94 Viper RT/10 <--Click
04 Ram SRT-10 <--Click SC!
05 Ram 4x4 Hemi FOR SALE
02 TA WS6 Collector Edition. K&N, lid, SLP Y, Magnaflow, Superchips

Ive used 5w30 and there was no difference on how the MDS performed.

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2006 1500 QC SLT Big Horn 5.7L Hemi,
K&N CAI
Edelbrock headers
custom Y-pipe
Dynomax Ultraflow Catback
Superchips
Alpine head unit,speakers,subs and amps.
Lucas synthetic oil.
65 Mustang coupe 289 V8,C4 trans
05 Yamaha Banshee

No, I was referring to all HEMI's, sorry.

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2008 Ram 1500 Big Horn Quad Cab 4x4
5.7L HEMI (MDS), 20" Aluminum Wheels, Tow Package, Popular Equipment Group, Power Heated Trailer Tow Mirrors, Inferno Red, Chrome Side Steps, K&N Filter, Rhino Lining, Chrome Bug Guard

Well, I see the forum is still broken.

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2003 1500 QC Hemi
2006 Chrysler 300C
2008 1/2 Mazda Speed3