I have an '03 Explorer XLS 4.0L SOHC w/145k. I drive daily, and about 25k miles/yr. I live in upstate NY (cold winters!). There is a very small oil leak from the front seal. The OEM recommended oil is 5W-30. What are the advantages/disadvantages of using a different weight of oil other than OEM. I've heard of people doing this. I'm new to this site and just learning about oil. I need an oil change soon and just don't have the time at the moment to research the answer on this awesome site so I'm just asking the question. Thanks in advance for your feedback.