Bad Gas mileage

[Dinosaurdriftteam]

I have a 90 300zx and it is getting really bad gas mileage. I checked the codes and it said it was the o2 sensor. I changed the o2 sensor and it is still reading the same code 33.
Any sugestions?

[twinturbozxtacy]

there are two o2 sensors, do both at the same time. then start with a tune up(plugs, fuel filter, air filter, oil change) they only get around 20 mpg, its a sports car...

[Dinosaurdriftteam]

I will change the other o2 sensor. and will give it a tune up. I am getting about 9 mpg so I should be getting twice as much.

[twinturbozxtacy]

ha ha yeah 9 is bad, usually what i get when im flooring it all the time. whats the mileage on the motor? you should also check the compression.

[Dinosaurdriftteam]

The motor has 84,000 on it and I will try to check the compression

[t.mcginley.jr]

Yeah 9 mpg is like a Hummer H1 on the highway lol

What brand of O2 sensor did you use? If you used cheap ones they won't last long -- either get OEM Nissan ones or Bosch (real ones). I put a pair of some no-name brand ones in and they lasted about a month before the codes came back. I put good Bosch ones in and haven't had a problem since.

Other causes of high fuel consumption can be bad coolant temp sensor (cheap, like $23 on Z1), fuel temp sensor (also fairly cheap), bad pcv valves, old spark plugs, incorrect ignition timing, etc.

[ta0sum559]

a nice tune up with some weight shedding should help.