Something different Building for MPG.
Back to basics:
I don't know at what ratio you are injecting the alc. But keep in mind you are paying $6.32 per gallon if your $.79 is for a pint which is usally how it comes.
Andrew
I do not have specific numbers right off hand, but the amount of the alky injected is minimal, but since it atomized, it kills 2 birds, so to speak. It takes heat out of the intake charge, and it is flamable, so it burns in the cylinders.
The info I read is the the reduction in the basic fuel that you run, far outweighs the cost of alky, over the time. Said another way, it is cheaper to run the alky, that injects a certain boost pressure, to keep detonation at bay, then to have to run race fuel the entire time, (or 91-93 Octane if built for street) for the few times you get into the throttle.
I personally would build it for 87 Octane, so I can step to 91/93 when desired, and then top it with alky or water injection, so boost pressure could be turned up without going to race gas.