Oxygen sensor location in car

At what point does oxygen sensor performance start to decline? It’s hard to say because a lot depends on the condition of the engine. If a high-mileage engine is using oil due to piston ring, cylinder or valve guide wear, phosphorus from the oil will contaminate the oxygen sensors and accelerate the aging process.

The same applies to coolant that may be seeping past a leaky head gasket. 

As a rule, the service life of oxygen sensors in most 1996 and newer vehicles with OBD II should be 100,000 to 150,000 miles or more — assuming no problems that could cause the oxygen sensors to fail prematurely.

Function of oxygen sensor in a car

Oxygen sensors should only be replaced when it is necessary. Most late-model vehicles do not have a recommended replacement interval for oxygen sensors. Like other engine sensors, there’s no need to replace an oxygen sensor as long as it is working properly and accurately reading the oxygen content of the exhaust.  

It is generally assumed that as long as the Check Engine light is off and there are no O2 sensor codes, the O2 sensors are probably functioning as in

when to replace oxygen sensor

how to tell which oxygen sensor needs to be replaced