Motor oil and lambda probe

Hai Loide,
I have to change engine oil again. I've reached 105,000 km. And now the question of the day. What kind of oil do I use? Expensive and good shell oil or is Castrol oil enough for this engine? The composition was 5W40! Is that okay? Is my first Audi V8 oil change. I'm getting pretty dirty deflowered, so to speak! And then I'd have another question where I'm typing right here. Does my 4.2er have one or two lambda probes? I guess one, don't I? Because my baby has a push-like acceleration that's getting worse and worse. Meanwhile, the current consumption also starts to jump (2/3 liters). And somehow, I think the consumption is increasing!
So, you're already mama thank you and leave again,
Dave...