[1st K5]

Can't remember where I read it but, using premium fuel in the 2.0T gave about 10hp gain over regular fuel.
This apparently came from kis engineers.
Wonder if this applies to the new theta 3 2.5T engine. If so, this bumps up the hp to 300 +/-

 

[rcook55]

Likely no, not unless the computer has a map to take advantage of it. Usually you see this with E85. Will it hurt, no, will you get NOSstickeronthesidewindow like gains, probably not.

 

[1st K5]

From what I understand, the ecu detects octane and adjust timing accordangly.
According to manufacturer, we should use 87 0r higher.

 

[Stoberkins]

Good watch that explains fuel grades:

 

[Warrenite]

Higher octane fuel burns slower/detonates at a higher temperature resulting in higher overall power output per ignition cycle.