I have 2006 Holden (Opel) Astra and the owners manual says to use 10W30 or 15W40 in ACEA A3/B3 or A3/B4. That's it. No other viscosity is listed, and no other standards like API are listed.
First oil I ran was Valvoline DuraBlend 10W40 A3/B4 semi-synthetic, close enough. Followed by other name brand A3/B4 10W40s as they are cheap and plentiful here.
I also ran some full synthetic A3/B4 oils such as Castrol Magnatec 5W30, Shell Helix Ultra 5W40, and Valvoline SynPower 0W40. Still no great risk, as they still carried the correct Euro spec, even if a slightly different viscosity grade, mostly the winter rating - which is nothing in my hot climate.
Probably my biggest deviation was Mobil 1 5W30, which was a ILSAC GF-5 and Dexos1 oil, so completely off grade and off spec. But hey, years down the road, and I'm still driving the car.
First oil I ran was Valvoline DuraBlend 10W40 A3/B4 semi-synthetic, close enough. Followed by other name brand A3/B4 10W40s as they are cheap and plentiful here.
I also ran some full synthetic A3/B4 oils such as Castrol Magnatec 5W30, Shell Helix Ultra 5W40, and Valvoline SynPower 0W40. Still no great risk, as they still carried the correct Euro spec, even if a slightly different viscosity grade, mostly the winter rating - which is nothing in my hot climate.
Probably my biggest deviation was Mobil 1 5W30, which was a ILSAC GF-5 and Dexos1 oil, so completely off grade and off spec. But hey, years down the road, and I'm still driving the car.