[Big Dave]

Regardless of where you get the feedstock, E85 is generally a bad deal for the motorist.

E85 has about two-thirds the heating value of RUG. Heating value (not octane rating) is what turns the wheels. Yet E85 costs a good deal more than two-thirds of RUG, usually about 80% of the price of RUG. Bad deal.

Having only 66% of the heating value of RUG your engine will not make the same amount of power as it will on RUG, unless you enlarge the fuel pumps, fuel lines and injectors. Normally, this is irrelevant to a hypermiler/ecomodder until that one time you need some acceleration.

E85 does deliver 100 octane, but even the highest performance cars get by OK on 93 octane gasoline. To take advantage of the 100 octane, you'd have to increase compression to about 13:1 and pour on a lot of spark advance. Increasing compression is an expensive mod.


Increasing spark advance and compression unquestionably improve engine efficiency. According to my Marks' Handbook going from 9:1 compression to 13:1 compression should get you an 11% improvement in engine efficiency. In today's well sorted out engines an 11% increase is huge.

But this increase in efficiency comes at a price. High compression engines emit more NOx than low compression engines on a "per HP-hr" basis. EPA regs forbid manufacturers from emitting too much NOx so they sell you low compression engines. So don't look for high compression E85 engines.

E85 has a low Reid vapor pressure. That is at any given temperature, less of it vaporizes per unit of time. As such, it makes your engine a bear to start in cold weather. Indeed, this is why they cut in 15% RUG. Drag racers know that alky engines are difficult to start. E85 make good aviation gas as (like 100LL) it doesn't boil off in the fuel tanks at altitude, and light plane engines have powerful dual ignitions to get them started. But that is a lousy formula for car and truck engines.

Hotrodders can take advantage of the octane but everyday drivers cannot. Some states vigorously enforce anti-tampering regs. (Indiana BTW does not). The EPA views raising compression as "tampering."

I'm sure you've heard that fuel grade alcohol can eat up seals and diaphragms common in engine fuel systems. The alcohol-resistant materials are mechanically inferior and tend to leak. Higher maintenance costs.

Another thought: Gasoline and alcohol readily part company in the presence of water or water vapor. Fuel grade "ethanol" is actually denatured alcohol or else you'd have to pay liquor taxes on it. So they cut in 0.5% by volume methanol into it so it isn't taxed. As we pointed out methanol and ethanol don't readily evaporate. If spilled it is more like to soak into the groundwater than gasoline does. Ethanol (99.5% of the mix) only gets you drunk and the dosage for that varies. Methanol is toxic in very low dosages. Remember MTBE - an octane booster used int eh 80s and 90s? Everybody turned on it because inevitably somebody spilled some and it got into ground water. That'll happen with any liquid. The MTBE gave the water a funny taste. By doing so it gave away its presence. Methanol has no smell or (I am told) taste, so you could get a dangerous dose and never know it.

To sum up:
E85 costs more on a $/MMBTU basis.
Normal gasoline engines cannot take advantage of the higher octane.
Gasoline engines running E85 have to be de-rated
Seals and diaphragms are an issue
E85 promote hard starting - particularly in cold weather
E85 spilled onto the ground will get into drinking water and is toxic.

IMO, America is brain-dead to even consider E85.