'98 Jeep ZJ Grand Cherokee 4.0 189,411 miles
Out: Rotella T6 5W40/Napa 1085
In: Rotella T6 5W40/Napa 1085
Touch over 6 months/56xx mile OCI
Also changed out the O-rings on the oil filter adapter. 4.0 XJ and ZJ guys know what I'm talking about.
Was -20F the other day and my Jeep with 5w-40 T6 showed little hesitation starting. Even my folks' WJ (also a 4.0) started alright and I think that's got some sort of 10w-30 conventional in it, not sure why when we use 5w-30 in almost everything else