Although many E85 vehicle demonstrations have been made using off-road vehi­cles such as airplanes,10 snowmobiles,11 boats, and all-terrain vehicles, there are not currently any significant numbers of these vehicles operating on E85.

material compatibility

Some materials that are commonly used with gasoline-powered vehicles are not compatible with E85. These materials are degraded when in contact with E85 and cause leaks or fuel system contamination.13 Fortunately, there are many alternatives for these materials. Also, limited duration contact with E85 in many of these materials has shown no detrimental effects. Most degradation requires long-term contact with E85.

E85 can be used in both four-stroke and two-stroke spark-ignited engines. Four-stroke engines are widely used in on-road vehicles because they generally offer better emissions and fuel consumption than two-stroke spark-ignited engines. In countries with strict air-pollution standards, even most motorcycles generally employ this type of engine. The strict emissions standards are also contributing to more widespread use of four-stroke engines for off-road vehicle use, such as snowmobiles and all-terrain vehicles (ATVs).

Most four-stroke spark-ignited engines currently available today introduce the fuel into the air intake system, not directly into the cylinder. This means that the fuel will come into contact with the materials used in the intake manifold of the engine. Fuel also comes into contact with the engine cylinders and the fuel induction and storage systems of these engines.

Two-stroke engines are lighter and often have better power-to-weight ratios than four-stroke spark-ignited engines and are, therefore, often used in smaller vehicles or in cases where weight is a major design consideration.

Developing countries still widely use two-stroke spark-ignited engines in vehicles due to their lower costs and smaller sizes. Two-stroke spark-ignited engines complete a mechanical cycle in two strokes of the piston, or one engine revolution. These types of engines do not have separate intake and exhaust processes. Because of this, these engines produce power every revolution, leading to smaller, lighter engines. Unfortunately, this also leads to higher tailpipe emis­sions and problems with bypass, where raw fuel and air pass through the engine unburned. To help combat this, many two-stroke spark-ignited engines use crank­case compression to improve scavenging efficiency and to reduce bypass.

This means that in two-stroke spark-ignited engines fuel not only comes into contact with the fuel storage and delivery systems, the intake, and the engine cylinders, but also the engine crankcase and even the exhaust manifold. Further, residual fuel is left in the crankcase after the engine is stopped, leading to potential long-term exposure.

Unfortunately, to save weight, most of these engines use aluminum exten­sively in their blocks, leading to potential long-term corrosion problems. As described later, hard-anodized aluminum has been shown to be resistant to E85 degradation. At this time, the long-term use of E85 in off-road vehicles with two — stroke engines has not been studied.