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.[1][dubious – discuss] Multifuel engines sometimes have switch settings that are set manually to take different octanes, or types, of fuel.[2]