We ran into the situation with the Liberty CRD. They recommended odd 0W-40. Approved but not recommended was 5w-40. I used rotella 5w-40. Turned out the 0w-40 was spec'ed to meet CAFE mileage standards. Now there are lot of CRDs out there with trashed rockers at 80-110K on the clock. Speculation is that the thin 0w-40 oil and heavy egr use (more than the euro counterpart (they don't seem to have this rocker issue in europe)) is what is killing the rockers. I defeated the emissions early on and ran good oil( I'm using old fashion 15-40 CI-4+ now). Oil analysis look real good. Point is, don't trust Chrysler on this. Do your own research. The motives for why Chrysler recommends this oil may not be the same as the end user trying to get the most out of the vehicle. And if emissions are deleted, all bets are off.
0W has superior cold weather cranking and pumping performance vs 5W (per the definition of the vis grade). At operating temperature there is no difference between a 0w40, a 5w40, and a 15w40. They are all 40w oils the only difference is cold weather pump ability. I run a 5w40 in my truck, but if I lived in a harsh climate such as northern Canada or Alaska I'd run a 0w40 for the excellent cold weather viscosity.
I also would not run a 15w40 in an engine that calls for 5w40, especially if you live in a cold climate. I just noticed you live in Georgia so it may not be as big an issue but cold weather starts with heavier than specd oil can accelerate wear.
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