🔍 Key Concepts

• Lube oil properties and what causes air to be trapped in the oil • The difference between foaming and simple contamination (like dirt or fuel) • Effects of water or moisture versus solid particles on oil behavior

💭 Think About

• Which of these choices would most likely cause tiny air bubbles to be held and stabilized in the oil, instead of quickly rising and breaking? • Think about which contaminant changes the surface tension of the oil so bubbles last longer, instead of just making the oil dirty or thinner. • Does high temperature alone create foam, or does it mostly affect viscosity and breakdown of the oil?

✅ Before You Answer

• Identify which option directly affects bubble formation and stability in the oil, not just cleanliness or viscosity. • Ask: which contaminant is most associated in practice with milky oil and persistent foam in sumps and sight glasses? • Eliminate any options that mainly cause wear, thinning, or deposits but are not known for increasing foaming tendency.