Sharpshooter64

I have a 1990 300zx automatic Na , that has me spending a lot of money on gas, I'm only getting 10 mpg, I've changed all injectors, timing belt, fuel pump, alternator, and many more parts, I didn't change these parts because of the mpg, I just changed them because it was time, computer is giving is giving oxygen sensor codes but my z specialist mechanic says that he doesn't believe that the 02sensors is the reason why I'm getting bad gas mialeage? The works on a lot of z's I mean a lot he dynos the cars and everything but can't find the reason why such bad mpg, am I missing anything here withe the sensors, I have always believed that bad sensors = running rich= burning too much fuel. He says that not necessarily that's the case? Now what's your opinion, should I just change them anyways and please advise which ones I should buy, or other wise. The guy is good but this is just not jiving with me, I need some others advise, thanks

Skully

Does the car feel sluggish at all or anything?
So regardless of the fact that the mechanic thinks its not O2's...They are still throwing you a code...I would say you can try cleaning the connections first (and to add you can test them with a multimeter), and see if you get a code again, or just plain outright change them. I would recommend stock bosch sensors.

PredatorZ

You stated that you changed all the injectors, did you replace them with stock injectors ?