Which discoloration may indicate rust particle contamination in an oil sample?

Which discoloration may indicate rust particle contamination in an oil sample?

• A. Muddy, reddish brown
• B. Clear yellow
• C. Translucent pale
• D. Turquoise

Answer: (A)

Rust particle contamination in oil shows up as a muddy, reddish-brown discoloration because rust is iron oxide. When iron components corrode, the resulting oxide particles become suspended in the lubricant and scatter light in a way that gives the oil a dirty, brownish hue. This color is a clear visual cue that ferrous debris is present in the sample. Other colors don’t point to rust particles: turquoise suggests copper-related contamination or certain dyes, while clear yellow or translucent pale tones are more typical of oxidation, aging, or clean oil without solid rust debris. So the muddy, reddish-brown appearance best indicates rust particle contamination.

Rust particle contamination in oil shows up as a muddy, reddish-brown discoloration because rust is iron oxide. When iron components corrode, the resulting oxide particles become suspended in the lubricant and scatter light in a way that gives the oil a dirty, brownish hue. This color is a clear visual cue that ferrous debris is present in the sample.

Other colors don’t point to rust particles: turquoise suggests copper-related contamination or certain dyes, while clear yellow or translucent pale tones are more typical of oxidation, aging, or clean oil without solid rust debris. So the muddy, reddish-brown appearance best indicates rust particle contamination.