Well, you're both wrong, and Stumpy is right: It's an MDS engine, and correct oil is critical.
I have an MDS '07 hemi so being a know-it-all I ignored the manual and put my normal diesel-spec 10-30 in it and the manual calls for 5-20.
Guess what?
MDS quit working and as a result mileage went down.
Switched back to 5-20 and the MDS came back and mileage went back to normal.
This is the one exception I have found in my automotive experience where the manual and Engineers were 110% right.
I believe there is another exception and that's ATF-4, but I'm not going to be the guina pig.
LOL
We both aren't wrong.
The OP is smart enough to read the owner's manual and follow the manufacture's recommendation.
He came on here to get the back story and it was provided.
I have a 99 CTD with a 6 speed (one of only 135 made that year) and the manual calls for some very unique tranny fluid that you can only get at the dealer
