*An internal combustion engine uses air as its working fluid, the fuel is used to heat the air in the cylinder to cause it to raise its pressure and force the pistons down the bore. For an alternative fuel to make the equavelant torque/power it has to heat the air in the cylinder an equal amount. Thus, if the alternative fuel has a lower energy density, more must be used to get the same total energy. Luckily, alcohol requires less oxygen than gasoline to balance its oxidizing equation, so you can richen the A/F to make up for the lower energy density, and thus you are burning more fuel to get the same amount energy.
*Octane has nothing to do with the amount of ENERGY in the fuel, its the fuels resistance to pre-igniting and detonating (You probably knew that, I'm just setting up my point). A higher Octane does allow a higher compression ratio, but a higher compression ratio only increases the effiency of the thermal cycle, it also does not increase actual energy. Yes, increasing the thermal efficiency will help offset the inefficiency of having to burn more fuel for the same amount of energy. BUT, increasing compression ratio makes the engine harder to start, which is already a drawback on alcohol, its harder to start, especially when its cold or extemely moist. As well, to take advantage of this higher octane, requires you to rebuild your motor to raise its compression ratio, or for turbo vehicles, you could increase the turbo boost. You did not rebuild your motor to increase the compression ratio did you? Nor will the overwhelming majority of vehicle owners if they switch to E85. If you did, the vehicle could not be switched back to gasoline, unless you buy racing/aviation gasoline or spend lots of money on octane boosters. So, the discussion of octane is academic, unless it applies to E85/Alcohol only vehicles, which are not produced yet, as well, virtually no-one is modifying their vehicles to be E85/Alcohol only.
*For the most part, Alcohol does burn cleaner than gasoline. It does not produce HC emmissions, far far less CO/CO2 emissions, but it does produce NOx and a different emmission, Formaldahyde and several of its varations. The aldahyde emmissions are relatively low, but so was the lead of leaded gasoline and that proved to accumulate enough to cause alarm. As well, aldahyde's don't break down or scrubbed in the environment like CO/CO2 and HC's, they accumulate like lead. Burning cleaner has nothing to do with the energy the fuel produces, you can argue its efficiency, but its efficiency we can not exploit. Natural Gas burns extremely clean, that why we can use it as an open flame on stoves in homes and never suffer any effects of the open flame, Natural Gas won't get you more mileage (CNG is even harder to measure mileage, since it has to be stored under very high pressure).
*LPG has 92k BTU's per Gallon, a little more than E85 and a lot more than ethanol and methanol, but still less than gasoline. Comparing LPG is a little tougher, since its measured in Cubic Feet, not gallons.
*Your getting more than 20mpg out of a Ford Ranger had nothing to do with attributes of the fuel, you changed gear ratios and made the vehicle more efficient for the conditions you were using it, it was less efficient for other applications because of the new gear ratio. So if was used in another application, requiring the OEM gear ratios, it would be less efficient OR unable to perform the task at all, because it did not have the torque multiplication required for the amount of torque the engine produced. Nothing wrong with changing gear ratios, if it helps you, but it doesn't magically gain you something that wasn't there before, you make a trade-off, in this case you traded performance and capability for more efficiency in cruising down the road at low weight/load.
Remember, your motor was malfunctioning, thats why you got more mileage on E85. I was incorrect in the fact that I thought you should be getting almost less than half the mileage of gasoline, I was thinking back to figures and confusing ethanol with methanol figures. I think I threw out a figure of getting 48mpg on gasoline if your motor was working correctly. E85 sould have a energy density of 90.5k BTU's per gallon, about 72% of Gasoline. So, if I recalculate, if you got 25mpg on E85, you should have gotten about 34mpg under the same conditions with a properly functioning motor. You admitted your motor was malfunctioning and you didn't repaire it, which is probably why you got higher mileage on E85. I think thats realistic, especially since it was your EGR that was malfunctioning and causing pinging. That malfunction would kill engine power, most likely your PCM would respond with turning back ignition timing and severly reducing efficiency, but a alcohol based fuel would resist that pinging more, and allow the PCM to keep ignition timing at normal and return your lost efficiency.