The downstream O2's do nothing more than tell the computer if the cat is still working correctly. The upstream one is used to calibrate the fuel mixture.If your consuming fluids I'd get them all changed. Otherwise, just the forward ones will do.
Here's a list of what I've done thus far.
1. Changed the air filter
2. 2 stage fuel system cleaning
3. New plugs and wires (they needed to be changed just due to wear)
4. New fan clutch
5. All the scheduled maintenance
6. Reset using the key/bump starting method
7. Had the fuel system/pump checked
8. Nothing outstanding on the dyno.
I just find it strange that there's such a mystery surrounding this mileage issue. I mean the dealers have basically shrugged his shoulders on this and have never heard of such a problem yet I know 3 people who own Rams who have the same problem.
I just don't think its breathing enough and considering I had my lights conk out on a dark road, I'm just not a fan of Dodge/Mercedes electrical engineering.
Besdies O2 sensors aren't there also air sensors at the point where they used to put a carborator before fuel injection?
Also about how long does it take to change the upstream O2 sensor?