Heated vs non heated o2 sensor
 

I read the 02 sensor does not work till it is 300degrees. I cheaped out and replaced the heated 02with an unheated o2 on my tail pipe. Did this hurt my mpg? 94volvo940 wagen. sC

I would think it would delay initial function. That's about it unless you are having other problems since installation.

regards
Mech

Would the car run rich or lean while the o2 sensor was heating up. The engine seems to run fine. Sc

Probably just runs in open loop mode, which is likely richer than closed loop. It's running a pre calibrated ratio of air/fuel, rather than using the o2 sensor to adjust air/fuel on the fly to achieve the best ratio as you drive.