It depends on cars, and on quality of oil and on driving style/habits, I had a (German BTW) turbodiesel car where the on-board computer would tell me when the oil change was necessary, and it averaged every 30,000 to 33,000 km (which happened after a little more than one year). I changed car only when (12 years old) it was around 340,000 km without having ever had any engine related issue (and it was still running fine, I changed it only because a relative's car with only 80,000 Km became available).