Use in standard engines

Experimental
E85 has a considerably higher octane rating than gasoline — about 110 — a difference significant enough that it does not burn as efficiently in traditionally-manufactured internal-combustion engines.

Use of E85 in non-FFV vechicles is generally experimental, with some users recommending light blends as low as 20%, while others have successfully run 100% E85. The main attraction of burning E85, of course, is the lower price per gallon at the pump of E85 versus gasoline. Other advantages include the common benefits of renewable energy sources, such as less environmental impact and less reliance on foreign energy.

Modern cars (i.e., most cars built after 1988) have fuel-injection engines with oxygen sensors that will attempt to adjust the air-fuel mixture for the extra oxygenation of E85, with variable effects on performance. All such cars can burn small amounts of E85 with no ill effects.

Operating fuel-injected non-FFVs on more than 50% E85 will generally cause the check engine light (CEL) to illuminate, indicating that the ECU can no longer maintain closed-loop control of the internal combustion process due to the presence of more oxygen in E85 than in gasoline. Once the CEL illuminates, adding more E85 to the fuel tank becomes rather inefficient. For example, running 90% E85 in a non-FFV will reduce fuel economy by 33% or more relative to what would be achieved running 100% gasoline. (This example is again for the same 1998 Chevy S10 pickup for which the fuel economy was studied in the controlled experiment mentioned previously.) Even more importantly, continuing to operate the non-FFV with the check engine light (CEL) illuminated may also cause damage to the catalytic converter as well as to the engine pistons if allowed to persist. It just does not make good economic sense to run a non-FFV with amounts of E85 high enough to cause the CEL to illuminate.

Under stoichiometric combustion conditions, ideal combustion occurs for burning pure gasoline as well as for various mixes of gasoline and E85 (at least until the CEL illuminates in the non-FFV) such that there is no significant amount of uncombined oxygen or unburned fuel being emitted in the exhaust. This means that no change in the exhaust manifold oxygen sensor is required for either FFVs or non-FFVs when burning higher percentages of E85. This also means that the catalytic converter on the non-FFV burning E85 mixed with gasoline is not being stressed by the presence of too much oxygen in the exhaust, which would otherwise reduce catalytic converter operating life.

Nonetheless, even when the CEL does not illuminate on the non-FFV burning E85, proper catalytic operation of the catalytic converter for a non-FFV burning higher percentages of E85 may not be achieved as soon as necessary to prevent the emission of some pollution products resulting from burning the gasoline contained in the mixture, especially upon initial cold engine start. This is because the catalytic converter needs to rise to an internal temperature of approximately 300 degrees C before it can 'fire off' and commence its intended catalytic function operation. When burning large amounts of E85 in a non-FFV, the cooler burning characteristics of alcohol fuel than gasoline fuel may delay reaching the 'fire-off' temperature in a non-FFV as quickly as when burning gasoline. Any additional pollution, however, is only going to be emitted for a very short distance when burning E85 in a non-FFV, as the catalytic converter will nonetheless still 'fire off' quite quickly and commence catalytic operation shortly. It is not known whether the small amount of pollution emitted prior to catalytic converter 'fire off' may actually be reduced even during the cold startup phase, as well as once catalytic operation commences, when burning E85 in a non-FFV. Likewise, even once the catalytic converter 'fires off', operation with the CEL illuminated will still result in excess amounts of nitrous oxide being released, greater than when operating the engine on gasoline. The solution is simply to add gasoline, and extinguish the check engine light (CEL), at which time exhaust pollutants will return to within normal limits .

For non-FFVs burning E85 once the CEL illuminates, it is the lessened amount of fuel injection than what is needed that causes the air fuel mixture to become too lean; that is, there is not enough fuel being injected into the combustion process, with the result that the oxygen content in the exhaust rises out of limits, and perfect (i.e., stoichiometric) combustion is lost if the percentage of E85 in the fuel tank becomes too high. It is the loss of near-stoichiometric combustion that causes the excessive loss of fuel economy in non-FFVs burning too high a percentage of E85 versus gasoline in their fuel mix.

E85 gives particularly good results in turbocharged cars due to its high octane [2]. It allows the ECU to run more favorable ignition timing and leaner fuel mixtures than are possible on normal premium gasoline. Users who have experimented with converting OBDII (i.e., On-Board Diagnostic System 2, that is for 1996 model year and later) turbocharged cars to run on E85 have had very good results. Experiments indicate that most OBDII-specification turbocharged cars can run up to approximately 39% E85 (33% ethanol) with no CEL's or other problems. (In contrast, most OBDII specification fuel-injected non-turbocharged cars and light trucks are more foregiving and can usually operate well with in excess of 50% E85 (42% ethanol) prior to having CEL's occur.) Fuel system compatibility issues have not been reported for any OBDII cars or light trucks running on high ethanol mixes of E85 and gasoline for periods of time exceeding two years. (This is likely to be the outcome justifiably expected of the normal conservative automotive engineer's predisposition not to design a fuel system merely resistant to ethanol in E10, or 10% percentages, but instead to select materials for the fuel system that are nearly impervious to ethanol.)

Fuel economy does not drop as much as might be expected in turbocharged engines based on the specific energy content of E85 compared to gasoline, in contrast to the previously-reported reduction of 23.7% reduction in a 60:40 blend of gasoline to E85 for one non-turbocharged, fuel-injected, non-FFV. Although E85 contains only 72% of the energy on a gallon for gallon basis compared to gasoline, experimenters have seen much better fuel mileage than this difference in energy content implies. Many automotive writers and columnists suggest that because of the lower energy content, you should expect an equivalent 39% increase in fuel usage. This has not been observed in practice when running gasoline and ethanol blends. Some of the newest model FFV's get only about 7% less mileage per gallon of fuel of E85 compared to their gasoline fuel mileage.

The reason for this non-intuitive difference is that the turbocharged engine seems especially well-suited for operation on E85, for it in effect has a variable compression ratio capability, which is exactly what is needed to accommodate varying ethanol and gasoline ratios that occur in practice in an FFV. At light load cruise, the turbocharged engine operates as a low compression engine. Under high load and high manifold boost pressures, such as accelerating to pass or merge onto a highway, it makes full use of the higher octane of E85. It appears that due to the better ignition timing and better engine performance on a fuel of 100 octane, the driver spends less time at high throttle openings, and can cruise in a higher gear and at lower throttle openings than is possible on 100% premium gasoline. In daily commute driving, mostly highway, 100% E85 in a turbocharged car can hit fuel mileages of over 90% of the normal gasoline fuel economy. Tests indicate approximately a 5% increase in engine performance is possible by switching to E85 fuel in high performance cars.

Experimenters who have made conversions to 100% E85 report that cold start problems at very cold temperatures can easily be avoided through adding 1 - 2 gallons of gasoline to the E85 in the tank, prior to the arrival of the cold weather.

No significant ignition timing changes are required for a gasoline engine running on E85.


Risks:
Prolonged exposure to high concentrations of ethanol may corrode metal and rubber parts in older engines (pre-1988) designed primarily for gasoline. The hydroxyl group on the ethanol molecule is an extremely weak acid, but it can enhance corrosion for some natural materials. For post-1988 fuel-injected engines, all the components are already designed to accommodate E10 (10% ethanol) blends through the elimination of exposed magnesium and aluminium metals and natural rubber and cork gasketed parts. Hence, there is a greater degree of flexibility in just how much more ethanol may be added without causing ethanol-induced damage, varying by automobile manufacturer. Anhydrous ethanol in the absence of direct exposure to alkali metals and bases is non-corrosive; it is only when water is mixed with the ethanol that the mixture becomes corrosive to some metals. Hence, there is no appreciable difference in the corrosive properties between E10 and a 50:50 blend of E10 gasoline and E85 (47.5% ethanol), provided there is no water present, and the design was done to accommodate E10. Nonetheless, operation with more than 10% ethanol has never been recommended by car manufacturers in non-FFVs.

Operation on up to 20% ethanol is generally considered safe for all post 1988 cars and trucks. This equates to running a blend of 23.5% of E85. Starting in 2010, at least one US state (Minnesota) already has legislatively mandated and planned to force E20 (20% ethanol) into their general gasoline fuel-distribution network. Details of how this will work for individual vehicle owners while maintaining automobile manufacturer warranties, despite exceeding the manufacturer's maximum warranted operation percentage of 10% of ethanol in fuel, are still being worked as of late-2005. However, the choice of transitioning to a 20% ethanol blend of gasoline is not without precedent; Brazil, in its conversion to an ethanol-fueled economy, determined that operation with up to 22% ethanol in gasoline was safe for the cars and trucks then on the road in Brazil at the time, and the conversion to a 20% blend was accomplished with only minor issues arising for older vehicles. Recently, conversion to a 24% blend was accomplished in Brazil.

In addition to corrosion, there is also a risk of increased engine wear for non-FFV engines that are not specifically designed for operation on high levels (i.e., for greater than 10%) of ethanol. The risk primarily comes in the rare event that the E85 fuel ever becomes contaminated with water. For water levels below approximately 0.5% to 1.0% contained in the ethanol, no phase separation of gasoline and ethanol occurs. For contamination with 1% or more water in the ethanol, phase separation occurs, and the ethanol and water mixture will separate from the gasoline. This can be simply observed by pouring a mixture of suspected water-contaminated E85 fuel in a clear glass tube, waiting roughly 30 minutes for the separation to occur (if it does), and then inspecting the sample. If there is water contamination of above 1% water in the ethanol, a clear separation of alcohol (with water) and gasoline will be clearly visible, with the colored gasoline floating above the clear alcohol and water mixture.

For a badly-contaminated amount of water in the ethanol and water mixture that separates from the gasoline (i.e., approximately 11% water, 89% ethanol, equivalent to 178 proof alcohol), considerable engine wear will occur, especially during times while the engine is heating up to normal operating temperatures, as for example just after starting the engine, when low temperature partial combustion of the water-contaminated ethanol mixture is taking place. This wear, caused by water-contaminated E85, is the result of the combustion process of ethanol, water, and gasoline producing considerable amounts of formic acid (HCOOH, also known as methanoic acid, and sometimes written as CH2O2).

In addition to the production of formic acid occurring for water-contaminated E85, smaller amounts of acetaldehyde (CH3CHO) and acetic acid (C2H4O2) are also formed for water-contaminated ethanol combustion. Nonetheless, it is the formic acid that is responsible for the majority of the rapid increase in engine wear.

Engines specifically designed for FFVs employ soft nitride coatings on their internal metal parts to provide formic acid wear resistance in the event of water contamination of E85 fuel. Also, the use of lubricant oil (motor oil) containing an acid neutralizer is necessary to prevent the damage of oil-lubricated engine parts in the event of water contamination of fuel. Such lubricant oil is required by at least one manufacturer of FFVs even to this day (Chrysler).

For non-FFVs burning E85 in greater than 23.5% E85 mixtures (20% ethanol), the remedy for accidentally getting a tank of water-contaminated E85 (or gasoline) while preventing excessive engine wear is to change the motor oil as soon as possible after either burning the fuel and replacing it with non-contaminated fuel, or after immediately draining and replacing the water-contaminated fuel. The risk of burning slightly water-contaminated fuel with low percentages of water (less than 1%) on a long commute is minimal; after all, it is the low temperature combustion of water contaminated ethanol and gasoline that causes the bulk of the formic acid to form; burning a slightly-contaminated mix of water (less than 1%) and ethanol quickly, in one long commute, will not likely cause any appreciable engine wear past the first 15 miles of driving, especially once the engine warms up and high temperature combustion occurs exclusively.

For those making their own E85, the risk of introducing water unintentionally into their homemade fuel is relatively high unless adequate safety precautions and quality control procedures are taken. Ethanol and water form an azeotrope such that it is impossible to distill ethanol to higher than 95.6% ethanol purity by weight (roughly 190 proof), regardless of how many times distillation is repeated. Unfortunately, this proof ethanol contains too much water to prevent separation of a mixture of such proof ethanol with gasoline, or to prevent the formation of formic acid during low temperature combustion. Therefore, when making E85, it becomes necessary to remove this residual water. It is possible to break the ethanol and water azeotrope through adding benzene or another hydrocarbon prior to a final rectifying distillation. This takes another distillation (energy consuming) step. However, it is possible to remove the residual water more easily, using 3 angstrom (3A) synthetic zeolite pellets to adsorb the water from the mix of ethanol and water, prior to mixing the now anhydrous ethanol with gasoline in an 85% to 15% by volume mixture to make E85. This absorption process is also known as a molecular sieve. The benefit of using synthetic zeolite pellets is that they are essentially comparable to using a catalyst, in being infinitely reusable and in not being consumed in the process, and the pellets require only re-heating (perhaps on a backyard grill, in a solar reflector furnace, or with heated carbon dioxide gas collected and saved from the fermentation process) to drive off the water molecules adsorbed into the zeolite. Research has also been done at Purdue University on using corn grits as a dessicant. [3] Once the ground corn becomes water logged, the corn grits can be processed much as the zeolite pellets, at least for a number of drying cycles before the grits lose their effectiveness. Once this occurs, it is possible to run the now water-logged corn grits through the natural fermentation process and convert them into even more ethanol fuel.

Running a non-FFV with too high of a percentage of ethanol will also cause a lean air fuel mixture. A lean mixture, if allowed to persist over considerable periods of time, will cause overheating of pistons and will eventually cause engine damage. It will also cause premature catalytic converter failure. This is also why the check engine light will illuminate if you mix more than around 50% to 60% E85 by volume with your gasoline in a non-FFV. If this happens, just add more 87 octane regular grade gasoline as soon as possible to correct the problem. (Some premium blends contain up to 10% ethanol; to correct the problem as quickly as possible, always add regular grade gasoline, not premium grade gasoline.) These lean mixture problems will not happen in a properly-converted vehicle.