My 2006 E90 has 10 months left till COE expiry. It is consuming 1 liter of engine oil every 2 weeks (roughly 800 to 1000 km). The engine bay is dry. I have white smoke coming out when ramming the accelerator. I understand that the cost to repair will be more than $1000+ even if I go to JB.
I am prepared to keep topping up engine oil every 2 weeks. Total costs will be roughly 20 liters of engine oil. I am presently using Mobil 1 0W-40 which is quite expensive. I was at Giant and saw that they have a promotion on Shell Helix Ultra 5W-40 for $39.90 for a 4 liter bottle. On the back, it says BMW LL-01. I have a few questions:
1) Is Shell Helix Ultra 5W-40 approved for BMW E90?
2) Can I mix Shell 5W-40 with Mobil 0W-40?
3) What are the differences between using 5W-40 to 0W-40 especially in an old engine that has sludge built-up and disappearing engine oil?
4) What possible problems could arise within the next 10 months if my plan is to just top up engine oil?
5) Any other suggestions and advice are welcome. Thanks.