new passat engine oil & light sensor!

Hello, can anyone tell me is its ok to use castrol GTX Magnetic engine oil
for the new passat petrol engine? My friend got a diesel and she was
told to use the long life engine oil only!,sold at the dealer. Is this just a gimmick ,so that you have to buy the oil from them or do they really mean it?

My light sensor on my car seem to be too sensitive?
It sometimes comes on even in broad daylight, or if i go into a tunnel and come back out the light still stay on! Even though its sunny!!?
Can it be adjusted?