Dr. Raj Shah and Stefan Lim, Author at Engine Builder Magazine
The Drive Toward Thinning Engine Oils

Oil viscosity has been on a thinner trend throughout the years. If you owned a car in the early 1990s, the engine likely used 10W-30, 10W-40, or 20W-50 engine oil, but cars today most commonly use 0W-20, 5W-20, and 5W-30.