Debunking common fuel economy myths amid rising pain at the pump

Laban Mwembi Nyaanga.

Kenyans have for months on end endured pain at the pump, with fuel prices hitting an all-time high in September last year.

At the time, a litre of petrol retailed at Sh134.72, diesel at Sh115.6 and Kerosene at Sh110.82 in Nairobi. But over the last five months, motorists have enjoyed some relief, with the Energy and Petroleum Regulatory Authority (Epra) retaining pump prices at Sh129.72 for a litre of petrol, diesel at Sh110.60, and Kerosene at Sh103.54 in the capital.

While the retail price is still high, things could have been worse were it not for the government’s intervention through the fuel subsidy programme, with motorists being spared Sh14.53 per litre on super petrol, which would retail at Sh144.25 without the subsidy.

The prevailing hard economic times have more than before increased the need for motorists to devise ways of saving on fuel, some based on long-held myths and theories.

Laban Mwembi Nyaanga, the technical training manager at Automobile Association of Kenya (AA Kenya), busts these myths and offers expert advice on how to get that extra kilometre out of your next fuel refill. 

Is it true that your car consumes more fuel in traffic?

Yes, in a traffic snarl-up, the driver will be in low gears, which require higher torque, thus increasing consumption. Additionally, movement will be slow, hence uneconomical fuel burning. 

Is warming up the engine necessary, and Does it affect fuel consumption in any way?

Yes, warming up is the engine is necessary whenever you are starting from a cold position. The combustion chambers need certain temperatures to burn fuel efficiently. Just like the human body functions well at a temperature of 36 degrees celsius, the engine block temperatures are usually around 80 degrees celsius. Consumption will be high in case operating at extremely low temperatures or overcooling of the engine. This is the reason the cooling fan is set to run intermittently and not continuously. Tear and wear on engine rotating parts also increases when the engine is cold. However, overheating also has the negative effect of pre-ignition, which may affect the smooth running of an engine.  

Male drivers are said to consume more fuel than women. How true is this?

False. In either case, this depends on the driver’s training and competency. If a driver does not engage the right gears, does not anticipate the road situation and maintain necessary acceleration, this will increase fuel consumption. Someone’s driving style, for example, rough driving, speeding unnecessarily and vehicle mishandling contribute to higher fuel usage. 

Is there a correlation between braking and acceleration habits and fuel consumption?

Yes, when a driver makes harsh acceleration, the engine revolutions go high, increasing fuel usage. This is usually witnessed when someone is overtaking and doesn’t have enough space hence making engine RPM (revolutions per minute - speed of the motor) to be extremely high. Harsh braking is associated with inattention to road conditions (failure to anticipate), and this means by the time a driver notices a situation to slow down or stop, they may have been at higher speeds, which basically results in a waste of fuel.  

What about turning on the air conditioner while driving? 

A car’s air conditioning (AC) uses a compressor that is engine-driven. This is an additional load, hence straining the engine and resulting in higher fuel consumption. The AC should only be used when very necessary. Otherwise, you increase fuel usage.  

What is the relationship between car servicing and fuel consumption? Does a well-serviced car consume less fuel?

Yes, tear and wear in a car result in higher fuel consumption. Well maintained parts ensure smooth-running. For instance, whenever oil, oil filter and air cleaner are changed, they renew the engine’s optimal performance as opposed to not changing these parts. 

Many people believe that you spend more fuel when you drive on low tyre pressure. How true is this?

Whenever tyre pressure is low, the friction between the road and the tyres increases, and therefore more traction effort is needed to overcome the friction in order to put the vehicle in motion.  

Does driving with the windows open affect fuel consumption?

Yes, vehicle body construction design takes care of aerodynamics to facilitate smooth penetration through air resistance. With windows open and travelling at high speeds, this creates more air resistance and drags the vehicle, hence more acceleration is required to overcome the drag. 

What is the impact of weight in the car on fuel consumption?

Every vehicle is designed with a particular capacity of load that is in relation to engine capacity. A vehicle needs torque and power to be able to move. Whenever there is more load, the torque and power also need to increase, and this increases fuel consumption. Driving a vehicle that’s empty will consume less fuel than when it is loaded. Overloading increases fuel consumption as well as tear and wear.