Do this test to see how much fuel you're actually using.

Cape Town - Just how honest is your car’s fuel consumption? Studies find cars use an average of 20% more fuel than its claimed consumption.

In light of this week's fuel price hike, your idea of how much fuel your car uses might be way off the mark.

This is according to Wesley Procter, general manager at used car retailer getWorth, who says that when it comes to fuel consumption, there are three versions of the truth - namely what the manufacturer claims, what your car’s instruments tell you, and how much fuel your car actually uses.

“It is very common to find that the amount of fuel you’re actually using is significantly different than your car’s manufacturer-claimed consumption,” he said. 

It's very difficult to replicate real-world driving conditions in a lab test, making reporting on the figures partly technical.

However, Procter says that the manufacturers also have huge incentives to declare as low consumption as possible. 

“The Volkswagen diesel emissions scandal has shown that measurement methods can be gamed,” he said. 

“With the fuel consumption test, there’s no need to break the rules to achieve an edge – the engineers know the specific parameters and can optimise the car’s design to score well under those specific conditions. Move out the specific conditions of the lab test, and fuel consumption quickly deteriorates.”

Here's how you can test and measure your car's actual fuel consumption: 
* Run your fuel down until your tank is half-full or less.
* Then fill up your tank to the brim and re-set your fuel counter and odometer (or write down your mileage).
* Drive until your tank is again less than half-full and fill it to the brim again. Now you know how many litres you’ve used and how many kilometres you’ve travelled.
* Divide the litres by the kilometres, multiply by 100, and you have litres per 100km.
* Now compare that to what your car’s instruments measured for that same distance and what your car’s claimed consumption is.

“It’s best to repeat this exercise several times to even out the measurements,” Procter said. 

“You may be surprised at how large the difference is. And naturally, the actual consumption is typically higher than what the manufacturer or your instruments claimed.”

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Cape Argus