Scheduled maintenance service items are determined by car makers through years of research. Engine oil and filter should be changed every 3,000 to 4,500 miles. Air filters should be changed every 12,000 to 18,000 miles. Your tires should be rotated every 5,000 miles. The 50,000 mile scheduled maintenance service adds four extra items to check or perform. The first is an inspection of the fuel system, checking for leaks. The exhaust system gets a complete inspection. The automatic transmission fluid and filter should also be changed. The vehicle’s suspension should also be checked for looseness and excess play or movement. Shocks and struts should be checked for leaks and function.
For more info, see How to Plan for Scheduled Car Maintenance