on the boards, everyone says that the NA's should use 87 octane, but a T2 should use the highest available octane (91 or 93 depending)? Just wanted to make sure.

 

Correct.

-=Russ=-

 

ok good, i just wanted to make sure...

 

So is a higher octane fuel just a waste in a N/A? I just wanted to make sure.

 

i've been using 87 octane since owning the car. It's an S4 TII. I'm not running too much boost tho, that's why. I think you need higher octane only if you're gonna up the boost a lot.

 

Complete waste... Unless you have LOTS of mods that would enable your motor to utilize the higher compression.

 

Compression?
The only differerence between octane ratings is that higher numbers have higher resistance to detonation. So a higher octane will allow you to run more boost or more timing advance.
If you don't have any way to modify those parameters in your car, then the higher octane is a waste.

 

The TII is also rated for a minimum octane of 87 R+M/2. Therefore, higher octane is also a waste of money on a TII that is running well and has no modifications that create a necessity for the higher octane.

Regardless of NA or TII, an engine that is not tuned well or in otherwise poor shape, or has been modified for much higher performance, may require a higher octane fuel to avoid knocking. Increased loading (ie traveling up steep hills, loading the car down with very heavy luggage, pulling a trailer, etc.) may also require higher octane fuel, especially when driving in places at low altitudes with very little humidity.