J Scoltock, Continuing combustion, Professional Engineering, January/February 2022, p 33

In the automotive world, Toyota together with Denso, Mazda, Kawasaki, Subaru and Yamaha are further exploring the use of hydrogen fuel in piston engines. Responsiveness with hydrogen is good because of the higher rate of combustion relative to hydrocarbon fuels, and steps have been made towards the thermal efficiency of gasoline and diesel engines.