What Happens If You Use Thicker Oil in Your Engine?

• Mr. Cong purchased a new automobile that requires an engine oil with a viscosity standard of 0W-20. He browsed around various automotive shops and heard them claim that "higher viscosity lubricant means better wear protection." To achieve the best possible protection for his new vehicle, he deviated from the 0W-20 recommendation and switched to 15W-50 oil instead.
• Next is John. He is an extremely cost-conscious individual, so he purchased a 1998 Toyota Corolla. It requires engine oil with a viscosity of 5W-30. However, he had some 10W-30 viscosity lubricant left in his garage, so he used it for his oil change to avoid the feeling of wasting good oil.

Engines are manufactured to operate with a specific viscosity grade of engine lubricant.

Thicker lubricant may not flow quickly enough.

Some differences in oil viscosity are less commonly publicized.