my 08 1500 manual says to use 5w-20 cause of the mds? but would it be that bad if i just used 5w-30, would it affect anything, and dont tell me whatever the manual says do it, cause i know that haha. but i thought id ask?

 

Internals are very oil viscosity specific in the MDS engines. I know if you have an engine failure in an MDS Hemi, Dodge will deny warranty claim if they determine any other viscosity is in there and you'll have a fight on your hands. Stick with the 5w-20...

 

dang haha ok back to canadian tire i go haha thanks tho Hammer

 

Yes, using anything but a 20 weight can be a problem mechanically on 5.7L MDS equipped vehicles. MDS actually operates in part using oil pressure and it is very important that you have the correct weight oil to do so. You can run a 0W-20 or a 5W-20 but the 20 is the important part( both will be 20 weight at operating temp which is what really matters ).

On MDS equipped 5.7L's when the computer goes into MDS mode the MDS solenoids open allowing high pressure oil to travel through special oil galleries to the lifters. There is a pin in the lifter that gets "pressed" by the high pressure oil flow. Once the pin is "pressed" it allows the lifter to collapse on itself rather than stay solid. You need a 20 weight for this to operate properly.

There is a lost motion spring inside the lifter that keeps it in proper contact with the cam and the push rod in contact with the rocker arm so nothing is loose but it isn't strong enough to keep the lifter rigid. So on the cam upstroke the lifter collapses on itself and doesn't raise up but it does remain in contact with the push rod. Because the lifter does not raise up with the cam the push rod doesn't raise up either so the rocker does not push down opening the valve.

The computer kills fuel and spark to the deactivated cylinders when MDS kicks in. As I understand it the intake valve never opens so no air is taken in. I believe the exhaust valve does open however to help make sure the cylinder is purged each cycle but I am not 100% sure on that.

There is more to MDS than just the part the lifters play but they are a crucial part of it all and for them to operate properly it requires a 20 weight oil. Hope this helps out.

 

The dealer will know if you put the incorrect oil in. Anything other thn 5w-20 and the PCM will detect the viscosity difference and store an "incorrect oil" code and can only be removed by the dealer via starscan tool.
Only use 5w-20.

 

5w-30 was prescribed for 03's and maybe 04's(?) before they decided on 5w-20 across the board.

 

ya i dont have warrenty anymore but i will still use the 5w20 to take care of my truck! thanks alot guys i appreciate it

 

3rd Gen 5.7L HEMI Ram oil weight recommendations...

2003 = 5W-30( 10W-30 allowed for in temps above 0 F ) ALL MODELS
2004 = 5W-30( 10W-30 allowed for in temps above 0 F ) ALL MODELS
2005 = 5W-20 ALL MODELS ( This was for CAFE reasons only - nothing mechanical requiring it )
2006 = 5W-20 ALL MODELS( required in 1500's due to MDS )
2007 = 5W-20 Ram 1500's( MDS )and HD's under 14,000lbs GVWR
2007 = 5W-30 Ram HD's over 14,000lbs GVWR
2008 = 5W-20 Ram 1500's( MDS )and HD's under 14,000lbs GVWR
2008 = 5W-30 Ram HD's over 14,000lbs GVWR
2009 = 5W-20 Ram HD's under 14,000lbs GVWR
2009 = 5W-30 Ram HD's over 14,000lbs GVWR