Multifuel
Multifuel, sometimes spelled multi-fuel, is any type of engine, boiler, or heater or other fuel-burning device which is designed to burn multiple types of fuels in its operation. One common application of multifuel technology is in military settings, where the normally-used diesel or gas turbine fuel might not be available during combat operations for vehicles or heating units. Multifuel engines and boilers have a long history, but the growing need to establish fuel sources other than petroleum for transportation, heating, and other uses has led to increased development of multifuel technology for non-military use as well, leading to many flexible-fuel vehicle designs in recent decades.
A multifuel engine is constructed so that its compression ratio permits firing the lowest octane fuel of the various accepted alternative fuels. A strengthening of the engine is necessary in order to meet these higher demands. Multifuel engines sometimes have switch settings that are set manually to take different octanes, or types, of fuel.
One common use of this technology is in military vehicles, so that they may run a wide range of alternative fuels such as gasoline or jet fuel. This is seen as desirable in a military setting as enemy action or unit isolation may limit the available fuel supply, and conversely enemy fuel sources, or civilian sources, may become available for usage.
One large use of a military multi-fuel engine was the LD series used in the US M35 2 1⁄2-ton and M54 5-ton trucks built between 1963 and 1970. A military standard design using M.A.N. technology, it was able to use different fuels without preparation. Its primary fuel was Diesel #1, #2, or AP, but 70% to 90% of other fuels could be mixed with diesel, depending on how smooth the engine would run. Low octane commercial and aviation gasoline could be used if motor oil was added, jet fuel Jet A, B, JP-4, 5, 7, and 8 could be used, in an emergency fuel oil #1 and #2 could be used. In practice, they only used diesel fuel, their tactical advantage was never needed, and in time they were replaced with commercial diesel engines.
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