I have a 2000 C280, 55m. At 44m, I needed a driver rear O2 sensor. Now I have code P0150, Bank 2, Sensor 1, or passenger front O2 sensor. Isn't the replacement interval for these more modern O2 sensors now around 100m? Looking at online pricing, the fronts are 30-40% more expensive then the rears, I assume meaning that all the parts are different even right versus left. I take it this means you can't use the generic O2 sensors available on ebay for ~$25? I just changed the O2 sensor on my 1991 300CE with a generic and it seems fine so far.

Thanks,

glenmore
2000 C280
1991 300CE
1990 LS400