Does jacking up a car's rear really fill up the fuel tank?

There are some photos circulating of cars at petrol stations in Johor Baru being jacked up at the rear end. Apparently, this helps fill up the fuel tank to its maximum. Does this really work and are there problems if this is done?

These motorists, who must look rather ridiculous to bystanders, believe that tilting the car liberates more space in the fuel tank. They can be seen spending several minutes easing the nozzle trigger, hoping to maximise the amount of petrol that can go into the tank.

The nozzles at petrol stations have an in-built mechanism that forces a trigger release when the tank is almost full. The fast-acting pneumatic release is activated the instant there is any splash of fuel at the mouth of the nozzle.

This is independent of the vehicle's attitude. If there is any vacant space left in the tank, the fuel will flow in rather slowly due to the frequent cut-off at the nozzle as explained above. This is because the filler neck's diameter is small and, as the tank fills, some splashback is inevitable.

The space in the tank will not increase, nor will a pocket of air be magically exposed by raising the corner where the fuel-filler is located.

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As a simple analogy, if you take a jerry can and tilt it any which way you can, there will be no means to boost its capacity.

Often, persistent triggering after the automatic cut-off causes spillage, which is drained away through an overflow near the filler - or worse, down the side of your car's bodywork, which could be damaging. In either situation, there is just pure wastage.

All those precious few millilitres of extra fuel you may manage to eventually fill is easier to gain by driving the car economically in the first place.

This article was first published in The Straits Times. Permission required for reproduction.