I did it anyway....
 

I ordered and installed both pre cat Oxygen sensors today.
The units I removed were 12 years and 98K miles old.
There were no CEL lights or poor running engine.
I just did it because they are not overly expensive, and I just had my
valve stem seals all replaced. I'm sure some oil has been burnt by my
BMW N62 engine. Some would say a waste of money, possibly so.
Either way you look at it, it's done deal.

I found great prices on exact Bosch brand, same part number on Amazon.
They were about a 100 dollars each.

I love my X5 and intend for it to last another 10 years.
That's 20 dollars a year for new sensors.

I prefer to change things prior to failure on some things rather than waiting until issues come up. No need to feel badly about or justify that. Good change if you ask me.

Engine has a steadier idle now.
Can't say scientifically it's better, but it
feels smoother to me.
Old units were dated original factory install.
Super easy install for my 4.4.
Guessing all 4.4, 4.6, and 4.8's are all pretty
much the same.

:thumbup:

In INPA.....you can monitor their values and performance.



http://i300.photobucket.com/albums/n...ambda_idle.jpg



In saying that, condition of carbon and soot/corrosion not really indicated.

It would still require to visually check and inspect overall condition.