Originally Posted By: SR5
GM / Holden / Opel Astra (AH)
Out: Local garage bulk, 10W-40 semi-synthetic & Z154 filter
In: Shell Helix Ultra 5W-40 GTL & Z154 filter
Out: Shell Helix Ultra 5W-40 (SN, A3/B4, MB 229.5, etc)
In: Castrol GTX 15W-40 (SN, A3/B3)
Same Repco Z154 filter.
I was going to do 12 months and 15,000KM on the synthetic SHU, but in the end I changed it after 3months and 4,000 KM. I think the oil and filter is still in good condition, that's why I'm happy to leave the filter in. But I changed from a high VI 40 weight oil to a lower VI 40 weight oil, to see if it warmed up quicker with my cold engine tick.
Once I run it for a bit, I'll report my findings here
http://www.bobistheoilguy.com/forums/ubbthreads.php/topics/4056672
That GTL oil, changed early, does seem to clean the engine up very nicely (looking through the oil fill hole).