Workshop: Fuel Consumption


Words and Images Martin Pretorius

No matter how lightly you’ve touched the accelerator pedal of your off-roader, it has never achieved the respectable fuel consumption figures claimed in the owner’s manual. It has actually never managed to come close to those numbers – not even when it was new.

And, while it’s easy to assume that the manufacturer misled you by adding a glow to the official figures, or that there’s something wrong with your vehicle, the blame actually lies neither with your right foot, nor with your vehicle, nor with the manufacturer. No, the problem really lies with the authorities. Government is the reason my vehicle uses more fuel than it’s supposed to? In a way, yes: not by physically forcing more fuel into the engine, but because they’re enforcing testing procedures which don’t reflect the driving conditions that you encounter on real roads. These procedures not only indicate how much fuel your vehicle is supposed to use, but also document the composition of the exhaust gas being pumped into the atmosphere. Because these tests indicate how much your vehicle pollutes the air, they play a pivotal role in determining your vehicle’s carbon-tax bracket, and the level of consumption-taxation in countries which apply that tax as well.

It all started back in the 1960s, when governments the world over first attempted to bring urban air pollution under control by issuing legal (if rudimentary) requirements for the tailpipe emissions of cars. Then, during the following decade, some drama in the Middle East led to two oil embargoes, which created a need for even more regulations, this time aimed at reducing the usage of a suddenly scarce commodity. Because exhaustemission testing was already in operation, it was decided to piggy-back the new consumption regulations onto the existing testing procedures.

That makes some sense… In theory, it should work perfectly, but reality and theory are unfortunately not
that easily reconciled. The emissions tests were initially devised in a process which involved environmental experts and manufacturers’ representatives deciding on a program for reducing tailpipe emissions which was acceptable to all parties. As the years passed, and the air became breathable again, the authorities were bolstered by their success. They began to implement ever-lower emission targets, and started implementing the newly-created fuel-consumption regulations around the same time.

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