Ethanol, but you need special permits to make your own. You can buy a conversion, you don't need to do anything to your vehicle, just reprogram the computer to inject more fuel, you can get a plug in to do that with.
only thing i've tried is a 60/40 mix 60 gas 40 e-85 seem to work okay to no ill destruction of my motor... so at the present time gas is 3.58 e-85 2.85 ... equals about $40 bucks saved each week on 100 gallon fill up (and I burn that much) and the sam milage... but if I go over the 60/40 mix milage goes down tried this on 4 differnt vehicles. (dailey trip is 110 miles)
93 ford explorer 4.0
96 chevy astro 4.3 vortec
96 chevy p/u 5.7 vortec
00 explorer 4.0 sohc
Methanol looks interesting. It looks like you need to drill out the jets in the carb, mess with the timing, use an engine with hardened valve seats, and run a catalytic converter (if you don't already have one) to clean up the emissions. Oh yeah, and in cold weather you'll need to start it on gasoline, or rig up a way to warm the alcohol up first. There's probably a good discussion someplace else.