The average new car isn’t much more fuel-efficient than older ones. Still, to this day, the average vehicle has a range of between 20 and 30 miles per gallon, a stat which was very similar in the 1920s. How come with all the advances we’ve made in the last century is fuel efficiency the same?

Question

The average new car isn’t much more fuel-efficient than older ones. Still, to this day, the average vehicle has a range of between 20 and 30 miles per gallon, a stat which was very similar in the 1920s. How come with all the advances we’ve made in the last century is fuel efficiency the same?

In: Technology

Answer 1

For a lot of mechanical and chemical processes advancement is logarithmic and not exponential. Think of it like this: 1 mol of octane when combusted releases 5150 kJ of energy. If operating at 3000 rpm an engine is firing for 0.02 seconds so each piston discharges 103 kN per mole, which at 100% efficiency would accelerate a 4000 pound vehicle at 56.8 m/s^2. But keep in mind that it per mol. A liter of pure octane consists of 6.15 mols of octane. So if we had a vehicle that operated at 100% efficiency and we were somehow able to fuel it with 100 octane gasoline, it would exert 31,672.5 kJ of work and with the average weight of a vehicle being 4000 pounds (1814.37 kG) there is a theoretical maximum we can get based on mass.