As per my limited knowledge, 0w-16 (and then 5w-16) is the oil grade, not 0w-15. IMHO, 0w-16 should exclusively be used in those engines, which have been designed and tested for it; and where this grade is also mentioned in the user manual.
If for 1KR-FE, 0w-20 is the minimum / thinnest oil grade which is also mentioned in the user manual; going below this grade may not be wise.
Secondly regarding change interval, won't Rs. 8800/4L bottle be costly for just 7000 Kms run?
I think, instead of buying Imported, Expensive Oils, why not go for Best Value for money? And local, reputed brands? Depending on different conditions and parameters in Pakistan, it may be a wise decision to change oil after every 5000 Kms, and not drag after it. One should select the oil too accordingly; neither too cheap, not too expensive.
Total Quartz 9000 Future Series (0w-20 and 5w-30 in particular) easily last more than 5000 Kms change interval and is also easy on pocket. Cost / Benefit ratio may be more for Mobil in the long run. Total Quartz 9000 5w-30 / 0w-20 4L bottle is Less than Rs. 4000.