My engine light came on and my car was running rough. I did a diagnostic

Hello, Thanks, No, when I drove it from the shop it was doing a little. I put a quart of oil in the car, I called and he asked me to leave over night. I took back and left over night, then the mechanic call me around 5:00 and tells me that he think its 02 sensor now because the computer is not registering the codes for him to see what the problem might be, but we can try it. I told him, N thank l will pick up my car. You asked why I didn't replaced #3, I asked him about replacing all the coils, he stated that it was only one bad #6. I informed him that the test stated it was 3 & 6. As a certified mechanic he say that it was only one #6, and I didn't need to do all. I paid over a lot of money for valve cover gasket, oil housing gasket and cool coil to replaced, and now he is saying I need 800 to replaced the 02 sensor. I feeling there may be an error in workmanship. I was told by my brother, everybody can't work on a BMW!!!!

Yes, BMW takes engineering to the edge, and throws some curve balls at technicians, but ignition coils, valve cover gaskets, and o2 sensors are standard for nearly every car after about 2000... I recommend getting a second opinion, and not using any mechanic that believes the o2 sensor would cause a failure to communicate with a scan tool.