RE: OXS Counter/Light
Along with what Mark said my understanding is that the mileage at which the
OXS light came on started at 30,000 miles, then went to 60,000 miles and the
O2 sensor was supposed to be replaced when the light came on.  Later years I
believe it went up to 90,000 miles.  This may well account for dropping the
OXS light as it was found that the O2 sensor didn't need to be replaced as
often as first expected.  BTW, all the above is based on what I've been told
by others on this list, hop I'm getting it right.