What kind of fuel? It actually doesn’t really matter. Kerosene, gasoline, diesel, jet fuel—the engine doesn’t really care; it just needs a heads up for what to expect so it knows how to start. “Once the engine starts it will automatically regulate itself to all of that,” says Alex Dzwill, Logos’ lead engineer for SilentHawk, adding casually, “it has a really complicated ECU.” Running on any fuel is a key facet for the military so that soldiers in the field can use whatever they find. Interestingly, Dzwill said that efficiency isn’t affected by different fuel.