I think Mobil 1 0w40 is an excellent choice for the LT1, it can be used year round in any climate. It's probably their best built oil next to their Delvac 1 5w40 fleet oil.

 

since I put the schaeffers 15w 40 in my oil pressure has always been around 45-50 warmed up.. thought I heard somewhere it bypasses the filter if its high just wondering if my oil is still being filtered, its still kinds clear and green but only been in for 150 miles.