Originally Posted by nicknaz
I am not so sure about the Mobil 1 5W30. I used that and Mobil 1 10W30 in my WRX and did oil analysis through blackstone labs and found that the oil sheered down to a lower viscosity after only 4000 miles and there were a lot of traces of wear metals in the oil.
My oil consumption was higher as well. I don't believe Mobil 1 5W30 is appropriate for a high heat turbo motor such as our N54
I switched to Castrol European Formula 0W30 and subsequently to Shell Rotella T and those were much more sheer stable under high temps and my oil consumption normalized, and wear metals in the analysis report reduced
Right now in my Z4 35i I am using the OE oil but if I were to switch, I would go back to European Castrol 0W30. There is a forum called bobistheoilguy where there is so much tech on oil, and this oil was highly regarded.
Coincidentally, BMW USA calls out specific oils that are approved for the engines and European Castrol 0W30 is one of them.
With no disrespect meant to the OP's mechanic friend, I would really want some strong tech before moving away from the manufacturer's recommendation. One example of such tech would be used oil analysis reports of the oil being recommended for the specific motor for a decent period of time from someone with similar usage pattern as you.
Reffering to their Homepage the Oil is BMW Longlife 04 certified.
According to the Z's owners Manual you can use Oil that is either BMW Longlife 01 or Longlife 04 Certified.
Now is there any difference? 04 is the newer standard, replacing the 01 to meet environmental regulations. 04 oils are "greener" than 01 oils hence there is less phosphorus and sulfide in it (substances used to reduce friction) can anyone confirm this? Alternatively I may use Mobil 1 New Life 0w40 which has BMW LL 01 certification.
Thanks for the constructive comments so far!