My truck has about 135k on it and since I don't have the previous owners maintenance records, I'm operating on the assumption that it is still on its original O2 sensors. So I was looking into replacing them.

What strikes me as odd, though, is pricing of the sensors

Both downstream sensors seem to be the same offset. Ok so far. Upstream are different part #s, which I assumed was to account for differing connector wire lengths or something. But then I saw the pricing. Passenger side is about $45, but the drivers side is twice that! This is consistent across brands and retailers. Both are upstream and heated. Both attach at the manifolds in the same location.

So does anyone have any insight as to why the prices vary so wildly?

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It helps if you identify what you're working on....

If the sensors are worn out or "bad", the computer will tell you about it. There is rarely a good reason to replace them if they are still working within acceptable parameters.

 

We just did both upstream 02s on a friends '11 Ecoboost (same PNs as 5.0 Motorcraft DY1184 and 1185) Rockauto.com had them for $47 and $53.... Drivers side has a much longer wire, ran up near back of block. Passenger side connector was next to trans.

As mentioned, are you throwing a CEL? We only replaced them as he was getting codes related to upstream O2s.

EDIT: took a screenshot but can't get it to post

 

No CEL. Main reasons I'm looking into it are age (probably ~10 years and >130k on those sensors), and a common sentiment that they should be changed every 60-100k; and gradually worsening fuel economy (<10mpg average).

Best case, I see some improvement in mileage due to it not running as rich; worst case, I gain some peace of mind knowing they're operating at full capacity and should be good for another 100k.

Still interested to know about the wonky pricing though. Longer wires don't really account for a 100% price difference

 

Where are you getting this pricing from? Almost every online retailer I've checked for PNs Motorcraft DY1184 and DY1185 (upstream left and upstream right) are within $10 of each other.

If you are going to dealers, ask to price match or just buy online. My 2 cents anyways.

 

Rockauto, Amazon, eBay, you name it...

'09 5.4 takes DY1120 (~$45) & DY1122 (~$90), as far as I can tell

 

Didn't realize you had a 5.4, assumed EB or 5.0... my bad. In that case, no idea what the deal is there on pricing.