I used Mobil 1 Synthetic ATF on mine. As long as your cap says "ATF only" on it you are fine with standard ATF (although i prefer synthetic). The 4.8's I believe use a different fluid, CH-11S if i recall, but its clearly marked on the cap.

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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