This one of those "been there...done that" topics. In my area, we also have 91 octane. I have found that no matter what type of cheap or high dollar octane booster I run with any combination of 87 -89, the car still runs like s.... I should mention, it is a 440 putting out close to 600 hp, so I never really expected it to run well on the lower end octane ratings. I did not seem to matter which booster I used, or for that matter how much I added. I added the booster to the 91 and believe I noticed a difference. More like running the 93. It is my opinion that the lower octane non-ethanol is crap. I believe that the tanks that it is in had ethanol in them at some time and that the H2O the ethanol absorbed ends up in the bottom of the tank. I always add ethanol/water remover and stablizer in the 91 and 93 only as a precautionary measure. I notice no difference when added, but I don't expect any difference, only if the car sits for weeks/months with the same gas in it. In this case, I believe the stablizer works and the ethanol eliminator adds protection with the crappy gas sitting in the lines and carb. It is my opinion that if you really want to maximize performance of a high performance engine, get your hands on some high dollar racing fuel. This is blended for high performance engines. Second choice, and much less expensive, is adding aviation fuel. Not sure of the ratio, but I tried 2-4 gallons in a full tank and the response was notably better, especially when using 91 octane. I think if we could believe the R+M/2 octane rating of 93, that would be all a street/strip engine would want. You have watch the ratio on AV to Pump. To much AV will through off the other chemicals found in Pump gas that is designed for our engines. I would not exceed a ration of 1:5. You can go more, but you would be better off buying racing gas. Bottom line is that the mix of AV will add 1 or 2 octane levels and smooth out most engines and get good performance out of them. It is much better than trying to figure out how many bottles of octane in a can is needed to do the same. Here is a quote I found interesting, and a chart that tells the story on Av/Pump mix. This is only my experience, here is a site that will answer your question from people that seem to be in the know. Sorry for it being a site that references vettes.
http://www.superchevy.com/how-to/car-care/1509-everything-you-need-to-know-about-octane/
Blending Race Fuel With Pump Gas
Adding a few gallons of race fuel to varying amounts of pump fuel is a popular octane-boosting method that enthusiasts use. We were curious what a race fuel expert would say about it, so we asked the Rockett Brand team. Here’s what they said:
“[Mixing race and pump fuels] is an okay thing to do, and much better than ‘octane boosters.’ It does not damage the engine, and improves the quality of the street gas. Octane numbers blend almost linearly, and we actually publish blending charts on our website for those who insist on doing this. For example, if you blend a 92-octane pump gas with a 100-octane race fuel in equal amounts, you will get a 96-octane fuel."
“Overall, I recommend that the user choose the octane that he or she needs, and not try to be a chemist and play with the fuel. Do you water down your drink before you consume it? Life is too short to drink cheap booze.”
