Oil for 2005 Grand Cherokee Hemi V8 5.7L

[Caiwu]

Motor China say this car only can use 5W-20 because its MDS valve train is sensitive to oil viscosity and flow rate.It is the first time I hear 5W-20 not for fuel economy but for function.What the Jeep company say about it over there?
Thank you.

 

[dave1251]

I have that in engine in my Ram 1500. It says the same thing. If you use an another viscosity the MDS will not work since it is dependent on the proper oil pressure to function. There is a TSB from D/C on it.