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What does a pink oxygen sensor tip indicate?

I have a 2001 Mazda Protege LX 2.0 with 121,000 miles. I removed the front oxygen sensor today to replace an exhaust pipe, and I noticed that the tip has a red/pinkish color on one side only. Does anyone know what this would indicate?

The only thing I could find online is that a pink tip indicates lead in the fuel. This is impossible, since the only gas station I frequent is a Conoco which is always very busy. Plus, I haven’t noticed any performance issues from bad gas, and not to mention the fact that leaded fuel has been completely phased out for 15 years. What’s weirder is that the sensor tip is only pink on one side - I’m guessing it’s the side that’s facing the exhaust manifold.

Anyone have any idea if this is something I should be concerned about?

I don’t know what a pink tip means, but unless you’re replaced it recently you might put in a new one, now that you have it out.

The pink color on the O2 sensor is from the additives in the gasoline you purchase. If you remove the spark plugs you’ll find that color on them also. Nothing to worry about.


But at 121K miles, a new sensor(s) is not a bad idea…They have a design life of 100K miles…