Stats: 98 4runner, 4 cyl, automatic, 2wd, 150,000 miles.
Question: what kind of mileage impact can the O2 sensor(s)have on the vehicle if one or both are bad. Neither has ever been changed. Nucklehead 1 (toyota service guy) says save your $ - just not necessary to change 'em. Nucklehead 2 (auto parts store guy) says Change 'em - could cause as much as 2 mpg loss or even more.
Also, what other kind of performance losses can they cause if they have gone bad?
Thanks in advance for the input.
