How to compare fuel consumption of cars
The Sunday Nation
Nairobi,
22 January 2012
Gladys Ooko is planning to buy a new car but she is concerned about the fuel consumption. She writes; “I have been offered two cars, one going for about Sh800,000 and the other about one million shillings. I checked their technical details on the Internet and found that the first car goes for 12km per litre of petrol while the second one makes 17km. Would it make economic sense to buy the more expensive but more efficient car?”
I think that Gladys is wondering how long it will take her to recover the extra Sh200,000 in the buying price through savings in fuel consumption. To find that out, we start buy working out the difference in the consumption rates of the two cars.
It is very tempting to simply subtract 12 from 17 and get 5km/L, but that would be the wrong way to go about it. The reason is that the given consumption rates are in km per litre and not litres per km.
The correct method is to start by converting the two figures to litres per kilometre. We do this by dividing one by 12 and by 17 separately. The answers are 0.083L/km and 0.059L/km respectively.
Now that looks reasonable: at 0.083L/km, the first car consumes more fuel that the second one. After all, 0.083 is greater than 0.059!
The next step is to find the difference between the two consumption figures; that is 0.083L/km minus 0.059L/km. This comes to 0.024L/km. This is the amount of fuel that the second car will save for every kilometre it runs on the road – just 24cc! At the current market price of about Sh111 per litre, this comes to Sh2.70 per km.
At this rate of saving, how many kilometres are required to accumulate the Sh200,000 additional purchase costs? The answer is simply 200,000 divided by 2.7; and it comes to about 75,000km.
The final question is: how long will it take to cover the 75,000km? That depends on your motoring habits. The best way to get a good estimate is to start by finding your average usage over a long time. Take me for example; I’ve had the same family car for the last eight years and in that duration I have clocked about 100,000km on it.
This works to about 12,500km per year, therefore it would take me about six years to save the Sh200,000. Is that a good financial decision?
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While on the topic of motor fuel; did the petrol station operators have a case in delaying their orders in anticipation of the reduction of the maximum retails prices? The answer is simply no!
Even though the price drop (Sh7) was greater than the retail profit margin (Sh4), the argument that the dealers were protecting themselves against possible losses doesn’t hold any water. The reason is that this apparent loss had already been recovered in previous price increments. And in any case, when the US dollar went below Sh90, any serious business person knew that the price of petrol would come tumbling down!
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