I have a Y reg Astra 2.2 SRi with 130k on the clock. It is using about 1 litre of oil every 1200 miles (about two weeks mostly motorway type driving) and doesn't appear to have any leaks.
Having read a few of the oil posts on here that doesn't seem to be as bad as I first thought, I can't actually see any oil being burnt at startup or after a run.
What I wondered was, am I better off topping up with 5/30 or 10/40 and is any brand regarded as being particularly good? I don't mind spending a few bob (but not on new guides or rings) to keep the motor going for a few more miles as I wish to change it soon but not yet.