Hi guys,
Thanks for the warm welcome to the forum. This is a nice place to get lots of info about our cars. Anyways I was wondering if there is any good reason why BMW says you should use castrol oils if possible. I'm stationed in Germany and cannot get fully synthetic castrol 5w 30 motor oil here. I can get Moble 1 fully synthetic 5w 30 so I will probably use that. Do you think BMW and Castrol have a deal together or is the oil actually the best to use in a bimmer for some reason. Thanks.

 

Probably a little of both. BMW probably has a deal with Castrol where Castrol provides BMW with free oil for development or something... so they'll ask people to use that in their engines in exchange... BMW probably designed and tested their cars with Castrol oil in the engine and so they'll continue to recommend the owners to use it. BMW also designs their cars under the use of Chevron Gas.. I read this back when it was the E39 not sure if it still holds true, probably still holds true, but does everyone use Chevron gas? Nope... I solely use 76 gas myself unless I cant find a 76 gas station.

You should be fine using Mobile 1. Thats good stuff. BUT dont mix them... make sure you drain the old oil out completely and try to flush it a little before adding Mobile 1

 

You're fine with any approved oil of the relevant BMW list (probably Longlife 04 list in your case)
BMW and Castrol have indeed a nice money spinning relationship. (apart from the fact that Castrol makes very good oils)

Here's the (january dated) Longlife 04 list. I also use the Mobil 1 ESP 5w-30 at the moment. Since January there were probably a few more oils added.