🔍 Key Concepts

• Fuel compatibility versus fuel quality – why mixing behavior matters when switching or blending heavy fuels • Simple onboard spot tests that engineers can do without lab equipment • What visual signs (layers, rings, separation) tell you about miscibility of two liquids

💭 Think About

• Which option describes a test that is practical, very fast, and requires almost no special equipment beyond what you’d normally have in an engine room? • Incompatibility of heavy fuels often shows up as separation or distinct phases – which test is specifically checking whether the two fuels actually blend together, rather than just having similar properties like viscosity? • Look for the choice that observes the appearance/shape of the combined fuels (for example, rings, layers, or clear blending) after they are put together in a simple way.

✅ Before You Answer

• Focus on a test that checks how the two fuels behave when put together, not just measuring each one separately. • Ask: does this test give a visible, quick result (e.g., rings, separation, or clear blending) that an engineer can interpret without lab instruments? • Eliminate any answer where compatibility is judged only by a single property (like viscosity) instead of the fuels’ actual mixing behavior.