As we've all learned this week, following Jay Leno's widely reported incident with a steam car that left part of his face burned, steam cars often use gasoline to fire the boilers that produce the motivating steam. However, that wasn't always the case, with gasoline coming and going out of fashion for steam car operators over the years and with some steam cars even fitted for burning multiple types of fuel.

Multiple outlets reported early this week that Leno, the former "The Tonight Show" host who currently showcases his and others' cars via his CNBC show "Jay Leno's Garage," suffered burns to his face on Saturday while clearing a clogged fuel line on a White steam car, one of several steamers in Leno's collection. Leno has told Variety that he is fine and "just need a week or two to get back on my feet."

The reports raised a number of questions among enthusiasts about the fuels used in steam cars. Even though steam cars are considered external combustion, do they still require gasoline? Weren't kerosene and other fuels also used to fire the boilers?

Yes and yes, according to Stanley Museum Archivist Jim Merrick, who noted that prior to 1910, Stanley cars used gasoline as both main fuel and fuel for the pilot burner. The Stanley twins, in fact, had pioneered not only the commercially viable steam car but also the use of liquid fuel - in their case, gasoline, at the time a byproduct of kerosene distillation that was widely available at drugstores for use in lighting lamps - in a steam car's operation. Prior to the Stanleys, steam automobiles used wood, as seen in the operation of the 1769 Cugnot fardier a vapeur or more commonly coal, as was the case with Sylvester Roper's Boston-based experiments in steam power.

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