The engine won't care whether its 5-30, 0-30, or 5-40 if just topping off with a quart


I'd be safe with a 5-30 but I have been using 5w-40 Rotella T6 since the vehicle had 40k miles - I also am in the South so I see some decent temps compared to Chicago in the summer

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2018 Ram 2500 6.7L Cummins 68RFE
19k miles -Bright White/Black - Big Horn Sport - Crew Cab Short Bed
2013 X5 35D (CEO's) - Born on 5/17/2013 -
82k miles - Alpine White/Cinnamon Brown/Premium Pkg, Sport Activity/Premium Pkg and Sound/20" Style 214/Running Boards