I now have 200,220 miles on my 2004 Corolla LE that I bought brand new on April 1st, 2004. I drove all highway miles each and every day. This car does not leak a single drop of anything and I consistently get 37 MPG (sometimes better).

 

I have never replaced the Oxygen sensors. Without the check engine light coming on and with no noticeable deterioration in MPG how do I determine that the sensors need replacing?

Or....should I just leave well enough alone and not mess with them until they crap out?

Thanks!!

From all I know they seem to last a lot longer than Jiffy Lube(franchises) says, and eventually you'll get a fault code, but I wouldn't replace it now unless you have a wave form test tell you that it's misbehaving enough to deteriorate your mileage.

I do hope you have exchanged trany fluid,coolant,plugs,and your brakes(inc. fluid)are probably due.

I do the tranny fluid every 40k or so, plugs at 105k, coolant at 100k, front rotors and pads at 165k. I've never replaced the brake fluid or the rear pads and shoes.

brake fluid is a time not miles item, every 2 years is suggested for most places due to how it absorbs moisture and can become acidic.

O2 sensors typically work correctly for about 90-100K miles, over that and they can become slow or 'lazy' due to eventual buildups of contaminants in fuel or soot and can cause lowered performance and lowered fuel economy long before an engine light may set.