Not going to matter 5W is 5W. It would not matter if iti was a 5W20 or a 5W50 they are going to behave like a 5W at test temp.'s! I run 0W40 and 5W40 dureing winter and summer and have no problems. FOr what it is worth I had Redline 5W40 in my engine one winter and it got down to something like -22°F or -25°F and the temp. when I got up to go to church was -18°F. My car turned over like it 70°F and fired right up. Their were only about 10 car's in the church parking lot that day. I would ignore any advice you get from someone saying that 5W40 is going to kill your engine but 5W20 is fine!