One of the most important aspects of engine maintenance is keeping the fluids the engine requires clean and fresh. The engine is the heart of the car, and its fluids are its blood. In your own body, your blood has kidneys and a liver to keep the blood clean — aside from the oil filter, a car engine can’t clean its own fluids. That’s why it’s important to change an engine’s oil regularly, and to make sure that change happens before the oil gets too dirty. Dirty oil in the engine is like dirty blood in your bloodstream. Things may go fine for a while, but eventually it will lead to disaster. Even small amounts of dirty buildup over time can lesson an engine’s lifespan.