Tintin bhai dekhen ismen i cannot help you much..
As PSO imports majority of the POL into the country.. Even we import petrol on shell's behalf.
Now i can tell you that the PMG imported is tested and is of 87 RON.. however "dandi" bhi mari jati hai..
PSO has stopped adding additives in the petrol we sell, thus the quality is reduced..
Total and shell (i know) add these additives thus charge a premium..
But we as individuals cannot test these claims at all. Nd moreover the company operated petrol pumps can be trusted only, to some extent.
So if you ask me which fuel is better.. I cannot tell u. But i can tell u 19/20 ka fark hoga.
I just make sure i refuel from company owned company operated pumps. As dealers dandi maarte hain theek thaak.