How can u tell when the oxygen sensor has gon bad

Do u have the computer hooked to a standard Ford issue diagnostic unit? If not, how is ur MPG? Are u stalling or does the engine hesitate?
DON't underestimate the local independant gas station near you. Just because the ''Today Show'' did the song & dance & ''proved'' all gas is the ''same'' do not buy the HYPE.
The station u patronize should fix autos. They should run STP additive as the current refineries r WAY behind upgrading & maitenance schedules in most US territories. Tell l am lying, my Lawyer is GREEK.
l used a very good degunker additive & my 67 mercury is tiptop despite my cheaply using a tank of subgrade Mcfuel from a Walmart adjacent petrol seller. Get to know ur local autoparts stores, find the one where they treat u like a regular at ''Cheers'' from TV. These places r real but not for anyone who is too enamoured of the ''shiny shiny'' NEW deals.
Larger cities r more likely to help those who drive Asian Autos, learn to fake a ''hickabilly'' dialect so as not to appear too ''worldly''. Worked for a Khan who does his own stunt work. Have a great Sunday.