Hi, relatively new here, and as I am overwhelmed with the amount of info available in this forum, I still am undecided as to which oil to put in my car. I drive a 1999 BMW 328i. I happen to live in Montreal, where the winters are deadly cold (-30 Celcius happens often enough) and summers get hot enough (30 Celcius once again). For the winter I use 0W30, otherwise the VANOS jams up and triggers a Check Engine light. The 0W30 is from Castrol, but I have no quams using Mobil 1 if it's better (or cleaner, etc.). Now for the 6 months of the year when we're not submerged in snow and hiding in our igloos I'm not sure wether i should continue using Castrol's 5W30 (OEM recommended - but I don't really trust BMW's recommendations as they tend to make you end up having to buy a new car) or switch to Mobil 1's 0W40 (which is also a approved BMW oil). I've performed searches, but I haven't really been able to assess what the main differences are between Castrol 5W30 and M1 0W40, their pros and cons. Thanks guys.