Next weekend, I'll have to change the motor oil, but I don't know which oil to choose.
According to Castrol website, I should use Castrol Edge 5w40, which complies with GM LL-B-025.
On the last oil changes performed at an Opel dealer it was used GM LL-B-025 5w30.
Which one should I choose now? Castrol Edge 5w40, that follows GM LL-B-025, Castrol Edge 5w30, that doesn't follow GM LL-B-025 or buy the oil at an Opel dealer?