What is the mileage on your engine?
If its 100k or more then better use 10w30 and any brand will do provided you change every 5000km.
If its 100k or less then better use 5w30 but if it burns oil then better use 10w30.
10w40 doesnt suit but if the owner has been using this grade oil for many years then better continue, and i would say go for Shell as its renowned brand than zic and there are less chances of 2 number or fake oil with Shell.
