As for engine oil capacity, yes 19 qts should be correct. If you want to double check it, climb underneath to look for a sticker on the driver's side of the oil pan. With P/N and engine S/N, call Cat at 877.777.3126 and they'll tell you how many quarts it should. Then after you change oil, mark the dipstick accordingly.
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Also, very important, when you're talking to Cat, ask them if your engine has a grease fitting on the fan assembly. I don't think so, but if it does and you don't grease it, your radiator fan will go out someplace in the middle of no where. I think Cat eliminated the zerk a couple years earlier because no one was greasing it and they replaced it with a permanently greased fan hub bearing.
I don't remember where I found the Cat S/N, maybe someone else can chime in as to where it's at on a C7
Bill