Wa Alaikum Salam,
First of all, Heartiest Congratulations on your purchase! 
Engine oil grade / viscosity may also depend on odometer reading. For engine oil, use any local / imported brand with the conditions that; oil must be 100% genuine and original, its API rating must be SN (not SM or below it), it should be fully synthetic and its grade / viscosity should be 5w-30 (preferable) or 5w-40 (Max). All these 04 conditions must meet!
I personally use eneos in my Passo, 2013 model. Oil is made in Japan and is performing extremely well, so would recommend it. Otherwise, you may use any other brand, but, avoid ZIC!
Regarding Islamabad registration, either you should have some property in Islamabad or a letter from your employer, i.e. proof of property / residence or employment are required.
If you live in Lahore and your vehicle will be mostly used in Lahore, well personally, I won't advice you to get your vehicle registered in Islamabad due to many problems which you might face in the future. Its also being said that vehicles registered in provinces other than Punjab / Capital, will be required re-registration in Punjab in the coming months. Do keep this thing in mind too. Registration charges are different for filers / non-filers due to different rate of W.H.T.
Regarding vehicle registration, procedure / criteria and the charges involved, merits / demerits of Islamabad registration by Lahore resident, you may google and also search on pakwheels blogs / forums. There are some posts and threads here, which clearly explain these issues.
I hope it helps. Thank you.
