Engine oil lubricates and removes heat from internal engine components. The oil filter removes harmful deposits from the engine oil, preventing them from being circulated throughout the engine.
Manufacturers differ in their recommended guidelines for when engine oil and oil filters should be changed. As a general rule, however, engine oil should be changed every 3,000 miles to keep the engine healthy and to prolong its life.
When changing or adding engine oil, follow the manufacturer's recommendation for the grade, often referred to as "weight" (0/30W, 5/30W, 20/50W, etc.), and type (petroleum or synthetic base) of oil to use. The grade based on the oils ability to flow - "viscosity". Using an incorrect type or grade may invalidate your manufacturer's warranty.
To change the oil and filter, the technician removes the drain plug at the bottom of the engine oil pan and drains the oil. The oil filter is then removed and replaced with a new one. The technician reinstalls the drain plug and fills the engine with fresh oil. The engine is started and checked for leaks. Finally, the technician switches off the engine, rechecks the the oil level, and resets the maintenance light.