Oxygen sensors

[kolb26]

I own a 98 4-door LS blazer with the standard 4.3. I currently have 40K on the odometer. What is the normal mileage interval before replacing the oxygen sensor(s). I believe there are two, one near the exhaust manifold and one near the catalytic converter. I recently aquired the vehicle from my deceased uncle's estate. Please advise.

Thanks,
C. Kolbosky

[The_ScareCrow]

There really isnt any specific time at which you need to change it, basically when it goes out. So, if you get a code then you need to replace it, other than that you should be ok.