I owned E83 since when I bought it new and now mileage is 60,000miles on it. My dealer in Japan suggested that I should replace the set of oxygen sensors with the new one as it is time to do so because the vehicle is eleven years old. To be replaced are oxygen sensor L=540mm and L=700mm, two oxygen sensor monitors L=990mm, all totalling over 160,000yen or approximately 1600 $. very expensive items. Is is normal for those oxygen sensors to be replaced with a new set around 60,000miles on it? If so is there any way to find another source to save my cost?
I wouldn't know options in Japan - there are lots of places in the U.S. that sell BMW parts; 02 sensors in German cars are typically Bosch, and presumably may be had for less. Not sure about 02 life span for later model BMW's, but older ones, just drive until they quit, and then the car throws a 'check-engine' light. At least on older BMW's, if the system works correctly, it registers a code for a faulty 02 sensor, and once the error code is confirmed and checked, then it's replacing an 02 sensor.
Normally 02 sensors are recommend to be replaced at 120k as per BMW. 60,000 miles seems a little early unless there is a issue with them.