NGK/NTK Oxygen Sensors = More MPG?

My car has 145,000 miles.

I recently changed the stock header and catalytic converter as well as installing a performance cat-back exhaust.

The car is a 1996 4 Cyl 2.2L Chevy Cavalier.

After installing the header and exhaust I noticed that my oxygen sensors looked pretty bad. Whiteish with some rust and somewhat dirty.

Has anyone used these or recommend them?

http://www.ngksparkplugs.com/products/oxygen_sensors/index.asp?mode=nml

The above link is for NTK Oxygen Sensors which claim they give better gas mileage than stock Oxygen sensors.

Here is what they say:

"Oxygen Sensors are used in modern automobiles to control the fuel and ignition systems to optimize a car's performance in the areas of emissions and fuel economy. Sensors are located before and after the catalytic converter to check on the amount of oxygen in the exhaust. The sensor sends signals to the car's on-board computer, which then can adjust several variables, including air/fuel ratio and timing, in order to bring the engine into the optimum operating range."

What do you guys think? Will this be a good buy?

Probably just a marketing gimick. Just get the obd o2 sensor that is correct for you car. Bosch makes most of the OEM ones but they're hiked up in price at the dealer so a Bosch unit from any retailer will work just fine.

if 2 different sensors are both reading accurately and switching within acceptable time frames, they are identical. If one is "getting better mileage" I would wonder what its doing less accurately/slower?

They'll only improve your mileage if your old 02 sensors are dying.

If your old O2 sensor set a code in the computer or is giving a high O2 reading, then your car would have poor gas mileage as it is. But if your computer hasn't noticed any fluctuations in the O2 sensor reading, then the sensor is most likely fine. What happens is that the sensor starts spitting out random numbers that are out of the possible range and the computer will clue in. Once the check engine light comes on, your computer will start using the standard fuel mixture in all modes of acceleration. THEREFORE, you will get bad fuel mileage. Now if your current sensors are fine, then the only way these new sensors will give you better gas mileage is if the indicate a lower O2 reading in the exhaust. What happens then is that the ECM will decrease the fuel going to the engine. However, that will shorten the life of your engine because you're running lean.