Different question so .. different question.

It's embarrassing to admit but after getting my car back from the idler pulley change and they'd disconnected the battery for whatever reason, it changed my normal display on the driving cluster from mpg to a new tripometer... so I didn't take time to read which gauge was displaying while driving and assumed it was mpg until the point it was way above what made sense.. haha >.<

I know the upstream oxygen sensor is needing replacement.. but could that account for 14.0-14.2mpg city? I don't floor it by any means and it's stop/go traffic in many cases so I'm not sure if that is really what I should be expecting. It's worth noting that the only codes being thrown are for the 02 sensor, backup camera, and rear wiper arm that needs replacement..

The O2 sensor is due to come over in the next couple weeks to a month (USA to West Africa). As I need to order most parts (if I want quality) from the USA, is there anything else I can look at to improve things? I'll actually be replacing both O2 sensors, did an oil change, coolant change (green to orange as needed), oil/air filters changed, etc.

Serpentine belt is also new now.. last one had a nice cut/hole in it about 1.25 inches long .. whole thing looked beat to crap but it's the original belt so no big deal.. Thing is, there is still a bit of a sound that was not there before when idling and I'm not sure if its a "break in" of the belt and pulley or if theres something else I should check.

It takes a while to get parts so I'd like to know now as I'm trying to order a few in soon..

Thanks!

p.s. my backup camera is still having issues despite them changing the main battery lead harness/wire group that had a grounding issue. They want to charge me to come back and have contacts sanded to remove corrosion.. is this something I can safely do myself? Are the wire connectors also something to target with a anti-corrosion spray of sorts?