Once a year for me I use it Mobil 1. ie thats if you do it yourself spend 50 dollars for oil and filter . Most car manufacturs are increaseing there oil change intervals from 3k to 5k or more. One example is my family owns a 98 ford explorer w/v8 motor oil change interval is 5k with conventional oil
. I was a little reluctant at first two when i saw the intervals on bimmers but i freqently check the oil and make sure it is not low and for one year or about 10k on my computer i have not added any oil. You might as well put conventional oil in if you are going to change every 3k 5k miles. thats my opinion you are just wasting your money.Synthetic when its designed for extreme conditions.
. Check and replace once a year is what i do and have not had any problems.