10W-30 Vs. 10W-40: What’s The Difference Between These Engine Oils?
Motor oil comes in a variety of forms, designated by pairs of numbers, but the most common two are 10W-30 and 10W-40. What’s the difference between them?
Source: https://www.slashgear.com/1807137/10w30-vs-10w40-engine-oil/