Sometimes I can't tell if you are stupid, or just plain retarded.
The only reason to get a higher grade (octane fuel) is if your car has a higher compression ratio and pings because of pre-detonations. There are charts and graphs, that can show you where the maximum efficiency/power/economy are and manufacturers will often try to build their engines around that point.
Adding supercharger, or a turbo supercharger changes the pressure/tempature in your cylinders so you will often need to upgrade your fuel.
The numbers you see ie 87, 89, 91 have nothing to do with watered down, or dirtier. It is simply the octane rating, how much pressure/temperature the gas can take before it self detonates.
If you are getting watered down gas, no matter what the octane rating, you are fvcked.
On a side note, you can mix gasoline, ie mix 87 with 89, to achieve a cheaper fuel mixture. If your car pings at 87, try mixing in some 89 if you are going to be doing some mountain driving, where your car will struggle ie pedal to the metal, put in a higher octane rated fuel. It is better for your engine not to ping. The higer octane fuel also does not burn as clean, and will emit more greenhouse gases ie co2, nox, co, etc
