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The drain plug is a 3/8" Dr. I too thought it was a torque, looking at it from the side and not straight on.
Some other things I'd like to share:
When doing my oil change, I remove the passenger front wheel well liner to access the oil filter. Never like having a armpit full of oil, I have a straight access through the wheel well, and over the frame rail. About seven 8mm bolts to remove, and then disco the one line that's clipped to the liner's inner edge.
Also... during all three oil changes so far, the filter o-ring likes to stay up on the housing once the filter is dropped down. Make sure that you check for this before reinstalling the new filter. This goes for any vehicle. If you have two o-ring seals, it will leak for sure.
Always coat the new filter's o ring with oil, to keep it from seizing on.
Remember... diesels take a little longer for the oil to drain back out of the block and into the pan. So allow it to sit momentarily before checking the level and assuming it's good to go.
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