I have a 2005 Town car and have always used 5W20. Car has 210,000 miles. On start up there is a very slight "clanking"noise for a second or two until the oil circulates. I have cases of 5W30 and 10W30. I was thinking of using the 5W30 in winter and 10W30 in summer. I think this would give added protection. Any thoughts. Thanks to all.