im pretty sure oil at the dealer are just rebranded castrol syntec 5w30. and the german 0w30 is actually a FULL synthetic oil that's better than the 5w30.

this is my oil change record:

8500km DIY castrol 5w30
17,000km DIY castrol 5w30
26,000km dealer free oil change
36,000km DIY castrol 5w30

so i think everything is ok. you should see how dirty the oil filter was when i did the first change. there're metal shavings on it clearly visible. i find it hard to believe an average bmw owner should wait until 26,000 kms for the first oil change.

Nope they didn't (according to Castrol themselves). I agree with the intermittent oil changes, but for the sake of saving a few bucks, it is not worth using engine oil that is NOT what the manufacturer would use. Your car - your choice. I wouldn't tell the dealer or BMW as it could affect your warranty if something goes wrong.

Sounds like a plan.

Why ask? Your mind is made up.

Oil threads are just a waste of time. (Which does not slow them down a bit.)

BMW 5W-30 is not Castrol Syntec as far as I know. It is apparently Castrol Softec TXT, based on the specifications, but I don't think we know for sure. It was rumoured to be Syntec in North America, since Castrol didn't sell the Softec here, but that seems to have been proven false.

Castrol Syntec is a full synthetic. Castrol Syntec Blend is not. Your post sounds like a Mobil 1 advertisement.

Where are you? Your oil suppliers likely have different oils than North America.

Give the 5W-20 oil away to some one with a Jeep 5.7 Hemi with cylinder deactivation!
That is the only good use for oil of this weight besides mixing with gas to burn brush piles!