Hello all,

This might be an extensive write, please skip to the last post for my question if needed.

Over the past week, I've been trying to gather everything I can about the o2 sensors in my wifes sc300. I so far have gathered that my year model has 4; 2 precat and 2 post cat. Most likely my 2 post cat are still good, but the 2 precat are commonly replaced? Correct?

The sc300 seems to have horrible gas mileage (note this is before getting the cel). Like a ridiculous 7-10mpg. My wife drives 2.5 miles round trip to work so about 15-20 miles a week accounting other little trips(most other trip to store, etc. we always take my car instead). We have to refill about midway through the second week or every two weeks. The car has about 240k miles. I just received code 21 for my main o2 sensor 3 days ago.

Since getting the car, I've mechanically
- replaced valve cover gaskets.
- replaced o-ring.
- replaced spark plugs and wirings.
- replaced head gaskets
- replaced distributor cap
- cleaned throttle body
- replaced air filter
- replaced alternator and starter

I have looked over CL extensively for the proper part numbers for the two precat sensors. I always find everyone suggesting denso this or universal one, etc.. no actual numbers even in the write up I found.

http://www.rockauto.com/catalog/x,ca...,parttype,5132
I plan on ordering from rockauto either the denso #2344626 or apwi #ap451. Am I correct in saying that these are the right ones for my 1995 sc300? Since I need 2 precat, am I simply just purchasing 2 units? What I want to make sure is that those are the right ones as I see other units listed there with the flanges that are listed for upstream when I can clearly see that mines on my car right now does not require the units with the flange. Lastly, anything I can do to improve my mpg?

Thanks for the long read and help.

Id sell you the two you need that came from my car (used but in perfect working order) for 40 shipped.

Mine is a 95 as well.

Thank you. I will definitely take your offer. Is there any problems with using a used o2 sensor? This has never really crossed my mind as o2 sensors as I understand it can not be simply cleaned or restored.

Any insight on this and for future reference if anyone can help shed some answers for me regarding my OP.

Pm'd you.

And just for transparency... the only reason they arent still in my car is that I upgraded to a wideband.(because im running standalone) They were in great shape, if memory serves, only have like 20k miles on them and worked as expected upon removal.