You should change oil every 3K miles or once a year, what ever comes first.
As far as all oils, they don't wear out. They get dirty. Almost all oils today have a detergent in them. Thus, they are made to clean. After about 3K the detergent breaks down and stops doing its job. That is why most recommend changing it at 3K (and not 35K).
Let me know if you have other questions.
Monday, March 16th, 2009 AT 3:39 PM