To get to the answer, they bought an old 1.6-litre Volkswagen Polo as a test subject and set a pre-modification fuel economy figure of 16.3km/L. They then removed the spare tire and jack, claiming to have saved 12kg and swapped out the old tyres for some new low-rolling resistant tyres. Lastly, they got the car a new Engine Control Unit which claims to be able to help optimise fuel consumption.
Guess how much fuel they managed to save? While this is no scientific test, it is still fun to watch and find out!