I replaced two of the four on my wife's Expedition. I used universal ones with different part numbers and the only difference was the length of the wires. It didn't matter anyway as I used some of the wiring from the old sensor.

I was told that an O2 sensor will start to go bad slowly until a code is sent. If your O2 sensors have over 75,000 miles I bet they can be replaced and you will see results.

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'85 300SD (formerly california emissions)
'08 Chevy Tahoe
'93 Ducati 900 SS
'79 Kawasaki KZ 650
'86 Kawasaki KX 250
'88 Kawasaki KDX200
'71 Hodaka Ace 100
'72 Triumph T100R