premium or regular?

Run what the owner's manual says and if you have problems with pinging or knocking run one grade higher.

Gen2 would be 87.

 

:thumb:

I ran 87 in my '99 for years but it started pinging last year so I switched to 89 octane and it's fine. Run the lowest (cheapest) you can without any pinging and it'll be fine.

 

Bonneville SSEi. Basically the same powertrain that's in the Grand Prix GTP. Supercharged 3.8 4 spd auto.

 

Cooper Mini's come supercharged out of the box.

 

I run 87 in my 2007. There is no need to run anything else. I tried premium and didn't feel any difference but my gas mileage was lower for some reason.

 

That's pretty common. Higher octane has to be harder to ignite (which is why it's needed for high-compression and blown engines), but it also is often slower to burn, and can drop mileage as a result, as the peak cylinder pressure shifts in time to a less advantageous piston placement (it's moved down too far already). For optimum toque output (and therefore both HP and mileage), you need to line that maximum burn point up with the piston just starting to move down by a few degrees of crank rotation (or maybe closer to 10-15º, it depends on the engine and a bunch of stuff). Different race fuels, in addition to having different octanes (resistance to ignition) also have different burn rates. So getting the timing advance correct, for a given fuel, at high rpms can drastically change output. But shell and sunoco might need different advances.

Ethanol is crazy high octane (116), and E85 is 100-105 depending on blend. This is why the saab engine with variable boost due to E85 or dino premium (93 octane) gains 60hp without loosing mileage when run with E85. It bumps up boost significantly, knowing the fuel will take it).

This is from memory, and it's late, and I think I remembered and understood all of that correctly. Someone will certainly correct me if I'm wrong. Most of this I got from an article on using Xylene and Toluene as additives to bump up octane in turbocharged cars. Both my WRX and the 350Z dislike the cali 91 octane, but LOVE Sunoco 100. My wallet doesn't love the Sunoco 100, though (it's UK territory for fuel prices). My '86 VFR runs best on 87. Noticeably crisper response with the more volatile fuel.