Bennit said:
1. Is brand really important or I must just concentrate on rating of the oil? I see plenty guys swear on Liquid Moly.
2. How many liters of oil should I buy?
3. Should I do a flush?
1. As long as it is a good brand, use what you prefer. Reading up can help you make a decision
2. check your owners manual to be 100% sure
3. not neccessary unless you missed a service or there is some issue with very thick oil or sludge.
I would take up the BMW special, around R1k for the 4cyl diesel, including oil, oil filter and labour.