Fuel consumption is a normal phenomenon with internal combustion engines in cars because they burn fuel to get the energy to propel a vehicle. However, fuel consumption becomes a concern when you realise that a car is consuming more than it is supposed to.
If you have noticed that your car is consuming more fuel than it used to, you may want to check on the following:
Paul Kaganzi, a mechanic and the managing director of Duke Car Technology, says if an engine is not tuned properly or the maintenance service delayed, “this will lead to a decline in the engine’s fuel efficiency.”
He adds; “When it comes to petrol engines, failure to replace worn out spark plugs, air cleaner elements or fuel filters as well as maintenance of the throttle valve and oxygen sensors will lead to an increase in fuel consumption.”
Meanwhile, “in a diesel engine, an increase of fuel consumption can result from dirty fuel injectors and air cleaner element as these two are crucial for prompt burning of the fuel during combustion.”
Poor engine oil
The quality of engine oil you choose to use in your engine can also affect fuel economy. Kaganzi says, “If you use the wrong motor oil viscosity grade in terms of being thicker than recommended, at certain temperatures or an inferior quality, the engine pistons and other moving parts move less freely. This adds a load onto the engine and hence a greater demand for fuel energy.”
Poor quality fuels
Nowadays, you can almost get fuel from anywhere as there are many kiosks and people selling it in bottles. Whereas this may be a life saver and even sometimes cheaper, mechanics say use of poor quality fuel can also increase fuel consumption. Therefore, be careful as you try to save because you may end up spending more. Kaganzi says if you buy adulterated fuel from dodgy road side kiosks, it will not burn promptly and would require larger amounts to move the car.
Some legitimate fuel stations have fuels that are mixed with chemical additives that clean the intake valves of petrol engines and injector nozzles of diesel engines to reduce accumulation of waste after burn deposits. They add a chemical which lubricates the upper piston ring and helps the engine move lighter with less fuel. This will improve fuel efficiency.
Peter Luyima, a mechanic and owner of Genesis Auto Garage, on Sir Apollo Kaggwa Road, says driving with the AC on adds an extra load to the engine hence it consumes extra fuel when operating. However, “if driving at speed of over 80 kmph, use of air-conditioning is better for fuel consumption than an open window as the latter creates aerodynamic drag. Also, if it is hotter inside your car than outside, when you start a trip, drive with the windows down for a few minutes to help cool the car before starting the air-conditioning. By first driving with the windows down, you will save on the amount of fuel that would have been used while the AC is on.
Worn out tyres
The general condition of your vehicle tyres can lead to an increase in fuel consumption. Kaganzi explains that when tyres are worn out, “Their grip or traction is lost so the tyre spins faster so as to move. This takes a toll on your fuel economy.”
Additionally, Luyima says poorly inflated tyres in terms of not putting the right pressure as instructed by the manufacturer will also lead to more fuel consumption.
He advises that you inflate your tyres to the highest pressure recommended by the manufacturer and make sure your wheels are properly aligned. Looking after your tyres will not only reduce your fuel consumption but also extend the life of your tyre and improve you vehicle handling.
Poor maintenance and short distance
Peter Luyima, a mechanic, says poor maintenance includes elements of delayed servicing and poor servicing which leads to overstretching of the service interval hence clogged air elements which lead to poor consumption range which in turn leads to more fuel consumption.
Vehicles are least fuel efficient and most polluting at the start of trips and on short trips. One reason for this is that catalytic converters (which reduce air pollution emissions) do not operate properly until they have warmed up.
Trips of less than five kilometres generally do not allow the engine to reach its peak operating temperature.
So rather than shopping at different intervals, plan to do a number of errands in one trip rather than several trips and save both time and fuel.
This mostly applies to manual cars because automatic transmissions will shift up more quickly and smoothly if you ease back slightly on the accelerator once the car gathers momentum. Certain speeds are supposed to be driven in certain gears. Luyima says if you are driving in gear number three, but are driving at 80km/hr, then you will need more energy to move the vehicle hence the vehicle consuming more fuel.
“Driving in a gear lower than you need wastes fuel, and letting the engine labour in top gear on hills and corners is also wasteful. In a manual vehicle, change up gears as soon as the car is comfortable with the higher gear but without accelerating harder than necessary,” Luyima advises.
Wornout clutch and warming the car in the morning
Most cars don’t need to be “warmed up” by idling before setting off. This simply wastes fuel. Start your car when you are ready to go. Once on the road, minimise fuel wasted in idling by stopping the engine whenever your car is stopped or held up for an extended period of time. By having the engine switched off, even for a short period, you will save more fuel than is lost from the burst of fuel involved in restarting the engine. The net increased wear and tear from this practice is negligible.
This causes wheel slippage especially when the car is starting or accelerating on wet or slippery road as power is not fully converted hence using more energy to move the vehicle which amounts to using more fuel. Slippage means insufficient contact between a clutch and pressure plate. Every driver of a manual vehicle must slip the clutch to move off or to move very slowly such as in very slow moving traffic or when performing a slow manoeuvre such as parallel parking for example. Slipping the clutch converts some of the engine power to be lost as friction.
Kaganzi adds that your driving style will also increase your fuel consumption. He explains that if you drive aggressively and do not shift gears quickly to the lightest one, this will keep your engine revolutions high thus consuming a lot of fuel. He advises drivers to learn how to use features such as cruise control and over drive to improve fuel efficiency.
The same advice also goes to people who suddenly stop while driving. “Drive at a good distance from the car in front so you can anticipate and move with the flow of traffic. This helps you avoid unnecessary acceleration and repetitive braking that ends up wasting fuel.” Kaganzi explains
Meanwhile, Luyima advises that if you see traffic stoppages ahead, first take your foot off the accelerator and let the engine’s drop in power slow the vehicle. He explains, “Don’t continue driving at the same speed and applying the brakes at the last minute. Getting back to cruising speed while the car is still moving uses far less fuel than stopping and then starting again.”
Over loading and speeding
Overloading will also increase your fuel consumption because the load puts an energy toll on your engine.
Peter Luyima, a mechanic says vehicles are designed to be driven up to a certain speed. He explains that over speeding will lead to a higher fuel consumption. The higher the speed especially if above 120km/h, the more fuel you will consume.