Your Holden/Opel Astra requires an ACEA A5 oil, check the bottle for that spec in a 5w30 weight oil. Synthetic oil can either be 0w30 or 5w-30.
Yamalube motor oil
The recommended oil is SAE 5W-20
10W-30 motor oil is recommended for the 2005 BMW X5 automobile. When the automobile is being used in extremely hot climates 10 W 40 motor oil is recommended.
We have a 2005 Astra AH model with the Opel motor, apparently Repco do not stock the required Oil, it's a fully synthetic oil that is very light. Holden have it at $30 per/L and is Red in colour. I have been told by a number of people now not to mix these oils and to use the recommended oil for the car, so I am about to take a trip myself to holden.
For cars, the manufacturer recommended motor oil.
5w20
For 1.6 liter Vauxhall Astra cars the recommended oil choice is 10w 30. For higher mileage engines synthetic blends are also a good choice to help keep the engine clean.
10W-30 motor oil is recommended for a Montero sport, under normal conditions. When the vehicle is used in a very hot climate 10 W 40 motor oil is recommended.
The recommended type of motor oil for a 2007 Cadillac Escalade is 0w-30 Signature oil.
It is recommended to use 10 W 40 motor oil in a 2003 Chevrolet Tahoe engine. It is also recommended using 10W-30 motor oil in a very cold climate.
5w30 is recommended about 3.5- 4 quarts is normal
10w30