Oil weight vs protection question

[NYH]

Originally Posted By: demarpaint
Originally Posted By: A_Harman
The Pentastar doesn't have MDS.


Good to know, one less thing that can go wrong with it. LOL

Nothing wrong with the MDS System. Between my friends and I we have bunch of Hemi Ram's, our plant used to be owned by Chryslert before they screwed us a few years ago, that's a different topic. Ram's are one of the most common vehicles amongst us. The '06 to '08 Hemi Rams & Durangos (MDS) get a few more MPG then the '05 and older ones do. It's mostly highway improvements since that's where the MDS System kicks in more often. It's a good system. I get 11 MPH in the city where my driving is just as much stop as it is go and up tp 18 MPG highway @ 68 to 70 MPH. My Ram is a 1500 Quad Cab Short Box SLT 4x4, Hemi, auto, 3.92 LSD, tow pkg. It gets the same mileage as my '94 F150 Super Cab, 4x4 5.0L, auto 3.31 gears and my 87 Bronco 4x4, 5.0L, auto, 3.55 gears did. . . . .except my Ram actually has power and can tow my trailers.

 

[almost_heaven]

I have a 2010 Jeep GC with 5.7L Hemi, 10k miles. Two related questions: should I use 5w30 when towing?; will using 5w30 harm the MSD system?


Originally Posted By: NYH
Originally Posted By: 440Magnum
Originally Posted By: CATERHAM

IIRC truck mfters such as Toyota and Ford that recommend 20wt oil do also suggest 5W-30 for extreme duty applications to cover their buts.


Funny you mention this, because I just stumbled across the appropriate entry in the 08 Ram manual last week. Chrysler recommends 5w20 for all 3.7 & 4.7 Ram 1500 engine applications, as well as for all 5.7 applications less than 14,000 lb gross vehicle weight (with the footnote that Xw20 is critical for 5.7L engines with MDS/VVT). For any gasoline engine application over 14,000lb GVW- which basically means a Ram 2500 or 3500 with a trailer- then 5w30 is recommended. Technically no 4.7 should ever wind up at over 14,000 lb, so I'm sure that's the only reason it isn't called out as well. Were I thinking about pushing a 4.7 right to the limit, I'd go with a 5w30, 5w40, or 0w40 personally.


Chrysler recommends 5W-20 oil for two main reasons 1- to meet the CAFE standards like everyone else, 2- the MDS system in their Hemi vehicles that drops 4 of the cylinders to improve fuel mileage works with less resistance on the engine like flat cruising speeds without the vehicle having a heavy load or towing. The lifters are what controls the MDS system. They need thinner oil to do so. 5W-30 oil almost never lets the MDS system kick in. Their cars had the MDS system first then their SUV's and 1/2 trucks started using the MDS system in '06. My '05 Hemi Durango called for 5W-30. My '07 Hemi Ram calls for 5W-20. The 3/4 and 1 ton Hemi's trucks didn't have the MDS system so thicker oil can be used. My fathers '06 4.7L Dakota calls for 5W-30. Now I'm pretty sure all their gasoline powered vehicles call for 5W-20 oil to meet CAFE standards.