Hi Fern,
Normal maintenance schedule is 7,500 miles for oil change.
Oil change would not affect the muffler, but rather if vehicles are seldom driven, the muffler would tend to rust and deteriorate more.
Performance wise, oil condition would affect it slightly if the oil is used over its recommended mileage.
Generally oil changes are recommended more on mileage rather than timed. That would also depend on climatic conditions. Humid climates with low mileages are recommended to be replaced every 6 months.
Tuesday, May 5th, 2009 AT 12:48 PM