Thanks for the advice BillK...

I do have the tool and knowhow to replace the O2 sensors as I have been involved with mechanical things my entire life. My problem is I am now retired and have taken the same hit as everyone else so I do not like spending money where it is not necessary.

I did replace the sparkplugs at 60,000 miles (rec. 100,000) on the advice of an Indy mechanic and I picked up 2 MPG when I did...that was good advice. On that schedule, they are due again. I can see now I could gain a similar effect by changing the O2 sensors, I had not considered that before. Thanks for the good advice.

Question on the Rear O2 Sensors: It is my understanding that the Rear O2 Sensors do not send a signal to the DME for tuning and they are only there to signal a mass failure in emission control; therefore, they do not affect performance. If this is true it makes sense to leave them alone until they fail and trip a DTC and throw a SES light.

Is that a true statement?