Oh yeah we're talking about a termi cobra here I just realized I didn't make that clear.

 

Got a GT but I'm living at home right now and my parents don't like the idea of me having two cars.

 

well, I just went searching and I think the belt actually drives the alternator too. So that won't work, I wouldn't advise driving a roots blown car on 87 if its tuned for 93. I thought they were setup like the lightnings, where its just the crank and blower on the second belt.

 

What about 1/3 93 and 2/3 87 with a real light foot?

 

Yea, it'll run it's not like it'll explode as soon as it cranks, but it'll be much more prone to detonate when you accelerate up a hill or something. It's all up to the way you drive it. It's just real hard to drive a roots car and not boost it much, I DD a 00 lightning and I can't really drive it w/o it boosting. I wouldn't put 87 in my truck, but thats because I know how I drive.

 

The biggest thing is like what Teej281 said. You need to retune for 87 octane. You could probably get away with your formula you listed above, however I wouldn't put anything 87 in a S/C or turbo'd car. Plus, I think it would still run like crap with 87 keeping it below 2000 rpms.

 

Tell me more about methanol. I'd really like to run methanol and 87 if the kit isn't going to be $1000+.

 

Cant u just fill it up with 87 then put some of that octane booster stuff in there? or is it not the same? just throwing out ideas...

 

Methanol is used by those with blowers because it allows more timing and more boost to be run using pump gas. I think with running a roots blower you have to get a plate kit but im not sure. But its sprayed into the intake tract somewhere and its like an octane booster to help prevent detonation. And what you do it you tune when it shoots methanol into the intake tract to either mass air meter voltages or to the actual boost pressure itself. This allows it to not be constantly spraying, but when its needed it is there.

 

I'd say go 1/4 87 and 91 the rest. But naww, don't be greedy bro. Not your father or anything, but take care of what you have. I refuse to put anything less than 89 out here in CA. Chevron, Shell, 76, and Mobil 89 is the lowest/cheapest I go.
As for a suggestion you can sell your GT and buy a civic or whatever. In that you can put 87 alllllll day!