Noman bhai, general rule of thumb is to use fully synthetic till initial 40-60K Km, Then use Semi synthetic from 60K Km to 100K Km & from 100K Km onward, one should use only mineral oil. But irrespective of the above mileage ranges, if engine is weak, then synthetic oil should be avoided.
I personally have switched between several brands including Shell, PSO CNG, Havoline, Petromin Ultra7 & now Zic Hiflo Semisynthetic. Among all these, I have found Petromin to be the best. Unfortunately, it is no more available in the market. The drop in performance & increase in engine noise is very much noticeable since I shifted from Petromin Ultra7 to Zic Hiflo.