What i mean is that due to poor quality , fuel doesn't burn properly and instead it ignites especially when you add more fuel to compensate for the lack of power.
For example , i had lots of detonation in my boxer when the fuel was really bad , especially if it was |"mixed" with whatever the gas stations use to increase their profit or in cases that the octanes were less than they were supposed to .
You can try "dry" acetone from pharmacy store to improve fuel quality. Google will help ou determine the exact dosology with fuel quantity.
A quick search showed ...
add in tiny amounts from about one part per 5000 to one part per 3000, depending on the vehicle -- just a few ounces per ten gallons of gas. This comes to between 0.0003 % to 0.0025 % acetone maximum or approximately 1/15th of one-percent. Note that is around .78 cc per liter or one ounce per 10 gallons. Not more than three oz. per 10 gallons.
Another issue might be the additives they use in the fuel you use . I am guessing major fuel supplier might be Brazil or if not they probably mix the same as there. Look what i discovered....
In contrast, alcohol has been shown to be corrosive in an engine, yet they put THAT into gasoline. Alcohol in general is anti-mileage. Alcohol is no good in fuels. In Brazil, millions of engines and fuel systems were ruined by alcohol. Yet they are talking of doubling the amount of alcohol in gasoline.
Furthermore, alcohol increases surface tension, producing the opposite effect from acetone. Alcohol in fuel attracts water. This hurts mileage because water acts like a fire extinguisher. Some cars may run badly and even quit due to the incombustible nature of the water-laden fuel. We know of a dozen cars that recently stopped running due to water in the alcohol and gas mixture. In my Neon, it frequently has cut the MPG in half on trips when I take pot luck at the pump.
In below-zero weather, the water and alcohol can form abrasive, icy particles that may damage fuel pumps and clog injectors.