All "Normal" cars run fine on 87 Octane. I once read in a US newspaper that running on higher octane than the one recommended for the engine would cause the extra stuff to not get burnt properly and hence result in carbon deposits on cylinder heads.
Having said that, the regular gasoline in Pakistan is far from 87 Octane. Its supposed to be 87, but Pakistani sell adulterated gasoline here by mixing kerosine oil etc. in it to earn extra profit.
So our "Hi Octane" is really 87 octane (I think) at most! I would not be surprised AT ALL if Pakistanis sell the SAME grade gasoline at the stations with two different prices calling it Hi-Octane! If they can adulterate the regular gasoline, they might as well be adulterating the Hi-Octane as well.
In the US, I filled my 2001 RAV with 87, 89, and 91 Octane. In all cases, I got the SAME mileage and SAME performance. Why? Because when they sell you 87, it is really 87. The engine did not need any more than 86. So runnning it on 91 did not make much of a difference.
But Pakistan is different.