I am in the process of burning through an oxygen sensor every three months in my 1987 560sl. The engine is running well. All the spark plugs are white. Has a new fuel distributor.

I am using after market sensors that are about $45. Does this matter or is my engine burning oil and fouling the sensor. There is no indication of blue or black smoke.

Why would the oxygen sensor by carboned up and not the spark plugs?

Does the EGR have an affect on the amount of carbon in the exhaust? I have had problems with bad gaskets on the EGR.

Could someone please tell me why I am burning through an oxygen sensor every three months.

Has this happened to anyone else?

Any help would be greatly appreciated.