Its very old engine and I don't know since how long you are owning it.
Well if you want to clean it up, then use ZIC D5000 15W-40 or Delo Gold 15w-40 and run it upto 1500 km only. (Suggestion given by Xulfiqar bhai in many previous posts). This is diesel engine oil infact but will make the engine very much clean from inside.
Prices per 4L bottle are as follows
ZIC D5000 1850 (Diesel)
Delo Gold 1840 (Diesel)
On the next oil change, I'll suggest to use ZIC M (15W-40) or 20w-50 viscosity oils.
Prices per 4L bottle of 20w-50 are as follows
Kixx 2190 G1
Toyot Petron 2150
ZIC Hiflow 2080
Havoline 1860 CNG
Kixx 1860 Gold
Havoline 1780 Petrol
Shell HX3 1700
Carient Plus 1580 (Petrol)
US Motor oil 1440
Choice would be yours. @xulfiqar bhai hope you will read it.