Why do some old cars only have 1 oxygen sensor even if its a v6?

Question

Why do some old cars only have 1 oxygen sensor even if its a v6?

Answer 1

Because that's when fuel injection was newer and they just used 1 to control fuel to air ratio. Now, the purpose of multiple sensors is to know more specifically which bank is running rich or lean, and the downstream O2 sensors measure converter efficiency. Many of these things were not available in OBD1.

Answer 2

before OBD2 cars only needed one before converter

Answer 3

The O2 sensors was still new and expensive.  Also the computer could only handle so much data.

But as O2 prices dropped and the computers became more powerful, AND the emission law became more strick, they started using more O2 sensors.

Good luck...