i own a 2000 bmw 328i and i bought it about 2 months ago and i know that it gets synthetic oil in it so whats usually the factory recommended mileage for an oil change or maybe people who own these cars after how many miles do you get an oil change in it
it does use synthetic oil
i thought it was supposed to be every 15000 miles

Using any major oil company's synthetic 5W-30 oil, (like Mobil One or Castrol), the BMW Oil Service I should be at least every 15,000 miles. Service II should be at 30K, 60K, 90K miles, etc. If you want to change oil more often, Oil Service I can be done at 10,000 mile intervals. There is also a special synthetic oil filter available, probably from a BMW dealer. The oil filter should be changed with every Oil Service I.