yea, im sure using 89 will causing pre-ignition which is what im trying to avoid, but im trying to figure out if its better to use 91 (since gas stations here only offer 87-89-93) im thinking of using 89+93 mix.

So im guess im trying to find out if there is some evidence that using 91 is better than 93?

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07 BMW x5 4.8i