Select File and then Print from your browser's menu. For close inspection and comparison, pour a small sample of each onto a piece of white paper, as in this demonstration. An engine's pistons move at high speeds against metal surfaces and can generate temperatures in excess of 4,000 degrees Fahrenheit.
Engine oil is what keeps the engine from burning up.
Frequent oil changes are the cheapest insurance you can buy for safeguarding the longevity of your vehicle. Just as our bodies depend on fluids to stay healthy, your automobile requires several fluids to operate and to stay in good condition. You've probably heard that analogy before, and there is certainly truth to it. Without oil your engine couldn't operate. Without coolant it would quickly overheat and burn itself up.