What are signs of contamination

• A. Oil is clear and odorless
• B. Oil appears milky and foamy
• C. Discolored oil and acidic smell
• D. Oil is dark but odorless

Answer: (C)

When oil shows discoloration along with an acidic smell, it signals contamination and chemical degradation. Discoloration indicates impurities or breakdown products have entered or formed in the oil, while an acidic odor points to acids produced by oxidation and other chemical reactions. Together, these signs mean the oil has been compromised and may not protect or lubricate properly.

Clean, clear oil that smells normal would not indicate contamination. Milkiness and foaming typically point to water in the oil, which is a different contamination scenario. Oil that’s dark but odorless could simply be aged or degraded without the strong clue of an acid odor. The combination of visible color change and a sour or acidic smell is the strongest indicator of contamination in this context.