The accident took place on Sunday, while Leno was working on a 1907 White Steam Car in his Los Angeles garage. A fuel leak and simultaneous spark caused the freak fire to start.
Leno is famous for his love of cars — his collection boasts over 180 cars, from exotic cars to museum-grade artifacts.
The former talk show host is currently in a burn center in Los Angeles, where he is expected to remain for the next five to ten days.
Leno credits his friend Dave for saving his life, saying he jumped on him and smothered the flames. He sustained serious burns on his hands and face, but his eyes and ears are uninjured.