The Society of Automotive Engineers (SAE) classifies engine oils by the viscosity grade of the oil. For this, a digital system is used. Lower numbers correspond to thinner oils that flow more easily at lower temperatures, while higher numbers link to thicker oils that maintain their characteristics at a higher temperature. Maximum vehicle oils are classified into one of five viscosity grades: 0, 5, 10, 20, or 30. The first number in the oil grade represents low viscosity (cold start temperature). The second number specifies its viscosity at high temperatures (hot work). For example, 5W20 oil is a good winter oil because it flows easily at low temperatures and remains a lubricant at high temperatures.