Originally Posted By: MBS500
Originally Posted By: vinu_neuro
Some of the oil mfr's specs (oxidative thickening, piston deposits, sludge, wear, etc. are exceptionally demanding. Call me a cynic, but I want formal mfr approval to trust that the product meets them. And it's not like there's that much saving over M1 or GC on sale. Let alone ones like Amsoil that charge a significant premium.
550i is out of warranty anyway, so you do not need "official" bmw oil. Nobody stops you from running the two and compare uoa with TBN, to see if saving worth it.
Lot of guys run Redline which doesn't even carry API and don't sweat.
Secondly for example for me it is hard to catch 40 weight M1 or Castrol on sale here, so mag1 with free delivery rulez in this case.
But if it fails to hold up, you are the one left holding the bag. So skimping a few bucks on an oil that isn't tested and approved for your application is gamble. If you think saving a few bucks an oil change is worth the risk, then go right ahead. But I wouldn't necessarily advocate others follow your lead here, as I think vinu_neuro has made a good point.