How sustainable are fuel efficient cars?

Let’s start with the obvious. Improving the fuel efficiency of a car is the right direction to go. There are three ways I can think of why fuel efficiency is important:

  1. Saves the customer money

  2. Less carbon emissions into the environment

  3. Might indicate the quality of the engineering

The first and second points are straight-forward: less fuel use saves you money and less exhaust saves the environment. I don’t think anyone can make a sound argument against either of these two points. However, the third point is curious and will be explored further. Below is a table which outlines some popular cars, hybrids and sports cars in terms of their fuel efficiency, power and torque figures.


Fuel Efficiency (L/100km) Power (HP) Torque (Nm)

Toyota Prius (maximum performance)

(3 L/100km) (130 HP) (120 Nm)

Kia Rio (maximum performance)

(3 L/100km) (110 HP) (135 Nm)

Porsche 918 Spyder

(3.5 L/100km) (762 HP) (528 Nm)

Subaru Outback (2.0 L, petrol)

(5.7 L/100km) (150 HP) (350 Nm)

Toyota Landcruiser (4.5L diesel)

(11 L/100km) (300 HP) (439 Nm)

In January this year, I was driving a 2016 Kia Rio along the NSW south coast. Several times throughout my journey I was going up a hill, with the foot to the floor and the engine above 4000 RPM, and I was still losing speed. If a car doesn’t have the power to get up a hill, or make a highway overtake even while dropping to second gear and mashing the throttle, it somewhat defeats the purpose of dropping the engine size.

The point I am making is being obsessed with fuel efficiency can lead to underpowered, unsafe cars. Fuel efficiency needs to be carefully considered in conjunction with the performance of the engine. In my opinion, a car which does 5.7 L/100km with 150 HP and 350 Nm of torque is much more sustainable as an all-round form of transport than something with 3 L/100km making 110 HP and 135 Nm of torque. Cars are built for more than just the multi-storey carpark and should be treated as such.