The "w" in 5w30 and 10w30 stands for "winter." The first number before the "w" indicates the oil's viscosity at 0 degrees Fahrenheit. The lower the number, the thinner the oil. The second number after the "w" indicates the oil's viscosity at 212 degrees Fahrenheit. The higher the number, the thicker the oil.
So, 5w30 oil has a lower viscosity at 0 degrees Fahrenheit than 10w30 oil. This means that 5w30 oil flows more easily at cold temperatures. However, 10w30 oil has a higher viscosity at 212 degrees Fahrenheit than 5w30 oil. This means that 10w30 oil is thicker at high temperatures.
Overall, 10w30 oil is heavier than 5w30 oil.
