When do you need to change 02 sensors on LT1

Just saw what looks like a good deal on amazon for o2 sensors (27$ - AC delco) . Wondering when they need to be replaced. Engine is running fine, but 85k, maybe it's something I should consider. Possibly improve fuel economy?

Those things are always $27-29 on amazon. Change your O2s when they swing slowly; get a scan tool or a data logger (or find someone who does) and let that be your guide.

Typical range on the O2 sensor should is between 50 to 950mV, O2 sensors degrade over time and can report biased or bad information. At 2000 RPM look for about 5 crossovers per second, a regular scan tool may not pick up this because it gathers too much information at one time and updates slowly. For less than $30 each, I would install new ones, but that is just me.

You'll need a red wrench, more than likely.