Which Motor Oil is Thicker: 5W30 or 10W40?

Learn which motor oil is thicker: 5W30 or 10W40, and understand their viscosity ratings for optimal engine performance.

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10W40 is thicker than 5W30. The first number (5 and 10) indicates the oil's viscosity at cold temperatures, meaning 5W flows better in cold than 10W. The second number (30 and 40) measures thickness at high temperatures—40 is thicker than 30.**

FAQs & Answers

  1. What does the first number in motor oil ratings mean? The first number indicates the oil's viscosity at cold temperatures, with lower numbers flowing better in cold conditions.
  2. Is 10W40 oil thicker than 5W30? Yes, 10W40 is thicker than 5W30, especially at higher temperatures.
  3. When should I use 5W30 oil? 5W30 oil is ideal for colder climates or for engines designed to use this viscosity under normal operating conditions.
  4. Can I mix 5W30 and 10W40 oils? Mixing oils of different viscosities is generally not recommended, as it can affect performance.