Wanted to update this thread. I was too scared to put 15w40 in while my QX4 was my only mode of transportation but when I got the truck I put it in and the valve train noise disappeared completely.
I am now putting SAE30 "Heavy Duty Diesel" oil in and I have no valvetrain noise at all. When winter rolls around I will probably switch to 15w40 Delo.
SAE30 is cheap and its always in stock at Walmart