Most of the stations have 91 super unleaded gas around here. Is there much provable differnece between 91 and 93 Octane?

 

if your getting 93+ in the southern gulf states you can run a little more compression and have a slighlty meaner engine.

 

If you're pinging on 91 then you need to use 93. If you're not pinging on 91 then 93 will provide no additional benefit. It's mainly a matter of timing. Even with a higher compression engine if the timing is set to prevent pinging on 91 fuel then higher octane makes no differance. Setting the timing for 93 octane fuel with that higher compression engine will get you more power though in some ranges. Low throttle at low rpms isn't one of the ranges though. It is once you open the throttle and the pressure before compression starts rising that pinging starts to become a problem. That happens sooner with a higher compression engine.

 

it is my understanding that 91 is a blend with alchol in it and 93 is not blended.

 

It's all blended one way or another. No real rules how you get the octane. All depends on the refinery and how it is running on any given day. All they look for is the finished products meets spects.
They do put in propritary additives when the trucks are loaded. They all buy from each other, then the people on the loading racks put in the additives for whoever.

 

When out west last year I was running the 120 on 87 octane. Did have to pull a little timing out but I could get it to where it ran well and mileage did not suffer. It is all in the tuning.

 

Ohio is one of 4 States in the US that has no gasoline regulations...so the pump says 93 but who really knows. I can tell when I get a tank of fake 93 because my bike is fairly well tuned and is sensitive to it. I'll guess I get scammed here about 33% of the time. Because on fresh 93 the bike runs perfect. On crap gas I get decel backfiring and rough acceleration.

 

I never tryed anything else but 94 from Petro-Canada.