Gas with higher octane than an engine needs (for its manufacturer-determined compression ratio, timing, boost in turbo and supercharged engines, etc.) does not improve performance. In fact, because the higher octane fuel is less explosive, it will actually perform slightly worse.
To maximize performance and to minimize cost, one should use the lowest grade of gas possible, without knocking or engaging the anti-knock functions of the engines. Since modern engines won't knock enough to hear (precisely because of the anti knock circuit kicking-in before audible knocking occurs), one can only follow the manufacturer's recommendation and assume that grade of gas is working properly.
Putting 100+ octane aviation fuel in one's IS won't improve performance and will only drain the wallet faster.
If using higher octane caused an engine to perform more poorly then racing fuel would not be of a very high octane.
Higher octane benefits engines with higher compression, like racing engines. In an engine without the higher compression, high octane performs worse.
Stated another way: Say you had two identical engines, A and B, both with 11:1 compression ratios, designed and tuned to put out 100 HP on 89 octane gas.
Put 87 in A, and 89 in B. A's anti-knock circuit will kick in, so A will deliver 95 HP, while B will deliver its designed 100 HP.
Now, put 91 in A, and 89 in B. A will burn slightly cooler because 91 octane gas is less volitle, so A will put out 99 HP, while B will still put out 100 HP.
Now, add a turbocharger to both engines (boosting compression to 12:1), and put in 91 octane in A, and put 89 octane in B. A will be able to take advantage of the additional octane by burning hotter without detonating, so A will put out 105 HP, while B's anti-knock circuit will come on, limiting its HP to 100.