🔍 Key Concepts

• How different types of contamination (water, air, heat) change the color and appearance of lube oil • Typical visual signs of overheating in lubricating oil versus water or air contamination • How viscosity differences show up (or don’t) when two oils are mixed

💭 Think About

• When lube oil turns dark yellow and opaque, what does "opaque" suggest about light passing through the sample? Is that more consistent with tiny droplets, bubbles, or chemical darkening? • Think about what each option would look like in a clear glass bottle: what would water contamination look like? overheating? aeration? mixing viscosities? • Which option is most likely to give a uniform milky/cloudy appearance instead of just darkening or visible separate layers?

✅ Before You Answer

• Be clear on the difference between color change (darkening) and loss of transparency (becoming opaque or cloudy) • Consider whether small entrained particles/droplets or bubbles are more likely to scatter light and make the oil look opaque • Eliminate any options that would more likely produce separation into layers rather than a single uniform dark yellow opaque sample