Gas mixing into oil
 

Just purchases our 1st Audi for our 16 yr old and the O2 sensor (sensor2 bank2) needed replaced. DONE! Changed the oil and took it for a drive. Can back and checked the oil to make sure it was not over or under full and noticed it smelled like gas. Any suggestions on the problem? The ck engine light is out now, checked 5of6 injectors to make sure they read the same, they do but the 6th one we could not get to easily. Didn't get a reading on that one. The original owner ran reg low grade fuel in it but I put mid grade, could it be that or should we try injector cleaner in the car? It is a 2001A4 quattro 2.8 automatic. PLEASE HELP.

Possible one of the fuel injector is carbon up and dump too much fuel. You can do a check like putting a flat head screw driver to listen to the injectors to hear if all the injector is clicking like each other that's at idle. To listen put flat head screw driver on top of the injector make sure not the the connector. Most of the time if you have a clogged injector it will sound different from the other injector and the clicking noise sounds weaker.

Same problem here. Can this cause the vehicle not to start?

Yes it can but check your timing belt first