Some info on adding Ethanol from Wikipedia:
Most of the downsides and big changes are regards to E85 which is a whopping 85% Ethanol and only 15% petrol, as opposed to 5% Ethanol.
The Tesco chain of supermarkets in the UK have started selling an E5 brand of gasoline marketed as 99 RON super-unleaded. Price-wise it is cheaper than the other two forms of high-octane unleaded on the market, Shell's Optimax (98 RON) and BP's Ultimate (97 RON).
Using alcohol fuels like ethanol, however, requires certain adjustments in car engines to be fully operational. Engine modification is not advisable for cars that use ethanol fuels in low concentration of up to 20%. But for E85, which is the declared concentration as alternative fuel, and Ee95, which is designed for high compression engines, modification is needed. When gasoline-only powered vehicles are loaded up with ethanol fuel, its computer systems, designed to read limited amounts of oxygen (ethanol contains greater amounts of oxygen), can be destroyed, thus creating engine problems. So motorists must first acquire a fuel flexible vehicle (FFV) by buying a new one or modifying the old, before deciding to switch to the cleaner fuel alternative that is ethanol.
E85
E85 is usually used in engines modified to accept higher concentrations of ethanol. Such flexible-fuel engines are designed to run on any mixture of gasoline or ethanol with up to 85% ethanol by volume. The primary differences from non-FFVs is the elimination of bare magnesium, aluminum, and rubber parts in the fuel system, the use of fuel pumps capable of operating with electrically conductive (ethanol) instead of non-conducting dielectric (gasoline) fuel, specially-coated wear-resistant engine parts, fuel injection control systems having a wider range of pulse widths (for injecting approximately 60% more fuel), the selection of stainless steel fuel lines (sometimes lined with plastic), the selection of stainless steel fuel tanks in place of terne fuel tanks, and, in some cases, the use of acid-neutralizing motor oil. For vehicles with fuel-tank mounted fuel pumps, additional differences to prevent arcing, as well as flame arrestors positioned in the tank's fill pipe, are also sometimes used.
The use of pure E85 in standard gasoline car engines may void the manufacturer's warranty, disrupt oxygenation control in fuel-injected cars, and result in power loss. It may also interfere with proper operation of the catalytic converter.
E85 can also cause engine damage, since prolonged exposure to high concentrations of ethanol may corrode metal and rubber parts in older engines (pre-1988) designed primarily for gasoline. In the United States, post-1988 fuel-injected cars are designed to accept E10 fuel, and may be tolerant of higher concentrations of ethanol to varying degrees, usually at least 20%.
Another risk is that of water contamination, which can produce engine wear directly and through corrosive formic acid in the combustion process. Oil and acid neutralizer additives can counteract these risks.
After-market conversion kits, for converting standard engines to operate on E85, are not legal to manufacture in the United States without EPA approval. Converted vehicles also usually require emissions certification, which is often not economically feasible.
