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?