My local store that carried my favorite Shell Full synthetic oil does not seem to sell it anymore so I am switching to Mobil 1. My SUV is a 2012 Nissan Pathfinder with 18,000 miles and I want to stay within the 7,500 mile max OCI for warranty matters. The 4.0 V6 calls for 5w30 and my original plan was to use standard M1 5w30 although now I am thinking about running the M1 0w30 EXt fuel economy as it gets down to -20F from time to time here in the winter. So am I better off running the standard M1 5w30 in the summer and switch to the M1 0w30 in the winter? Or just stick with the standard M1 5w30? Will the M1 0w30 give me better cold starting or is the standard M1 5w30 just fine for my use?