02 Explorer requires 5W20. I have been using Mobil 1 for my oil changes and have been using 0W20 Mobil 1 from Wal-Mart because the oil bottle says that it is an acceptable substitute. Now I can't find the 0W20 Mobil 1 anywhere. Did they stop making it or am I looking in the wrong places? Is there an acceptable synthetic substitute? Thanks for your help.