Hmm... I've never heard of anyone mean thermodynamic efficiency when talking about fuel efficiency of a vehicle. Maybe people who design aircraft engines do? S

Hmm... I've never heard of anyone mean thermodynamic efficiency when talking about fuel efficiency of a vehicle. Maybe people who design aircraft engines do? See e.g: https://en.wikipedia.org/wiki/Energy_efficiency_in_transpor https://en.wikipedia.org/wiki/Energy_efficiency_in_transpor > The energy efficiency in transport is the useful travelled distance, of passengers, goods or any type of load; divided by the total energy put into the transport propulsion means.