So what does "W" mean | Passenger Car Motor Oil (PCMO) - Gasoline Cars/Pickups/Vans/SUVs | Bob Is Th
ozzman In 10W-30 oil, the two numbers mean it is a "multiviscosity" or "multigrade" oil that is effective over a range of temperatures. The first number, 10, is an index that refers to how the oil flows at low temperatures. The second number, 30, refers t...