Which Engine Oil is Thicker: 5W40 or 10W40? Understanding Oil Viscosity Ratings

Discover the difference between 5W40 and 10W40 engine oils and learn which is thicker at cold and operating temperatures.

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Both 5w40 and 10w40 oils have the same thickness when the engine is at operating temperature (indicated by the '40'). However, 5w40 is thinner at cold temperatures compared to 10w40, making it better for cold starts.

FAQs & Answers

  1. What does the number '5W' or '10W' in engine oil mean? The 'W' stands for winter, indicating the oil's viscosity at cold temperatures. '5W' oils are thinner and flow better in cold weather compared to '10W' oils.
  2. Are 5W40 and 10W40 oils equally effective at engine operating temperature? Yes, both 5W40 and 10W40 oils have the same thickness at engine operating temperature, represented by the '40' in the rating.
  3. Which oil is better for cold climates: 5W40 or 10W40? 5W40 is better suited for cold climates because it is thinner at low temperatures, improving cold start performance.

Watch More

To further understand engine oils and their impact on vehicle performance, check out our guides on choosing the right oil for different climates and detailed explanations of oil viscosity ratings.

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