I started puting 93 octain gas since I got the car like 5 month ego the oil is geting black to quick my dad says that my car dosent burn the gas all the way and the particles get in the oil.

Correct ? Can my car burn 93 octain ? if not what dose it burn ? the lowest one or the mid one ?

Or my oil is black beacuse of somthing else ?

Do u think if my car burns 93 octain it even makes a diff if I put that in ? But I do drive on a highway almost averyday so I was thinking higher octain will get me batter milage ?