Our local news in Mn had a reporter tell how important it is to get ready for the cold weather. He said to change your oil to 5w-30. He had a cup of 5w-30 and a cup of 10w-40 and said he had them outside for 3 hours. This was in 0f weather. He then poured out the 10w-40 and it was thick milky white. He then poured out the 5w-30 and it was cleaner looking and a little thinner. Then the anchor lady said " yeah, i'll bet that 5w-30 stuff is more expensive too". This shows how much people know or think about there oil.