hi sages- this may be a good one for kitty grey who was recently talking about O2 sensors. my92 245 has 240k and runs very well. has consistently during my period of ownership(about 4 years) delivered 25 mpg in town and about 32 on the highway. local 240 drivrs dont believe me but they all have automatics which may account for their lesser mpg. mine has the m47 with the 3d pedal. anyway for the last year my check engine light has been on. agents and uncle moe tell me this is usually caused by the O2 sensor in the exhaust pipe crapping out. some here say if the O2 craps the computer tells the fuel system to run rich. no deterioration in the driveability of the engine has been noticed nor has the mpg gone to hell. is this correct? im inclined to do nothing (to wit if it aint broke dont fix it). havent checked the obd 1 yet. would that confirm the death of the sensor? your kind advice is graciously sought. thanks tons oldduke