If you're buying 75 liters of 87 octane fuel at $1.29 per liter the cost is $96.75. If you calculate 10% of this as ethanol (7.5 liters) at 2/3 the BTU, this ethanol is roughly equivalent to about 5 liters of 87 octane gasoline without ethanol (.66 * 7.5). So, your 75 liters of fuel is actually more like 72.5 liters without ethanol. (75 - 2.5, or 96.6% of 75 liters of gas without 10% ethanol).
To find out if it's worth buying 89 over 87, simply take the cost of 87 octane per liter and divide it by .966. If it comes out costing more than one liter of 89 octane gas, fill up with 89.
I'm not sure but I think this means you have OCD. :clap:
However, while your information was interesting my point still stands that people will arbitrarily buy 94 octane fuel when someone else is paying simply because they think it's better, regardless of any metric used.
Apple laptops rarely have more than adequate GPU horsepower and their new ones are no exception.
... and overheating issues most times. All the more reason to drive that video chipset harder...