Quote:
Originally Posted by Eagleback
My 2013 and my 2017 cummins, Synthetic oil is NOT recommended unless in extreme cold temp where the ambient temp is 20 deg or lower. The dealer will not put it in and says it can void warranty.
I know im going to get slack from that statement but it does say it in the owners manual.
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Not in my manual ,nor the diesel supplement does it say what you are saying. What it does say is 5W-40 synthetic is recommended at below 0 degrees,
and 15W-40 above 0 degrees . Although 5W-40 can be run at the same temperatures above 0 degrees as the 15W-40 is ran at . In other words both can be run above 0 degrees , but only 5W-40 synthetic below 0 degrees .
The reason is cold weather starts at 0 or below.