Fuel consumption of a car is the inverse of fuel economy. Fuel consumption is the fuel consumed to travel a specific Kilometer which is calculated as Liters per Kilometer or gallons per mile. As the adverse effects of Climate Change ravage countries more and more people are choosing to buy more efficient cars. Globally, governments are imposing a ‘sin’ tax on car emissions, making citizens to opt for smaller efficient cars to pay less tax and enjoy higher fuel economy.
There are several key factors that influence how much a vehicle uses and how quickly it consumes fuel including;
- Weight
- Aerodynamics drag
- Engine parameters and
- Rolling resistance
It is certainly obvious that a semi-trailer towing a container has a lot of aerodynamic drag, and the weight factor will increase fuel consumption. In contrast a McLaren P1 has an aerodynamic drag of 0.34 and well distributed weight makes for better consumption figures as compared to the semi-trailer.
The reason the Continuous Variable Transmission (CVT) is very popular today is that;
- It can draw a lot of power from a small engine
- control the speed range
- produce fewer emissions and
- Light weight
The above reasons make them perfect for application in fuel efficient cars.
CVT gear boxes are being used with most entry level production cars, CVT is good with small city cars, hybrid cars or small cars with small power and torque outputs.
However, for big vehicles the normal automatic gear box is the best to use at highway speeds as it is more reactive and not slow to accelerate.
This brings me to the point that consumers are increasingly buying small hatchbacks that are designed as small city cars and they use them even for long commutes. These cars are designed for the urban city roads and they are optimized for this slow congested traffic. Some have CVT’s and during highway speeds their consumption dramatically increases which causes owners to wonder what the issue is.
A while back I had the pleasure to drive a 2000 Mercedes Benz w124 C200 to a place 480 Kilometers away; I filled the tank and started my journey. I drive at a high rate of speed so on that way I averaged 100-130 Km/hour and on getting to my destination the tank was almost half I had used only 28 liters.
In contrast I went to the same destination in a small city car Toyota Vitz 1500cc, I filled the tank and I got there having used 35 liters of petrol. On this journey I averaged 100 Km/hour as it was the safest speed as the car is too light and would rattle every time, I overtook a truck. This journey taught me that it is better to have a normal sedan on a highway as compared to a small city car.
If we explore Diesel cars, they are always considered to have superior efficiency as compared to Petrol engines which use about 60% of fuel the rest is exhausted. The difference maybe the price difference of both fuels at the Petrol Station as well as the new emerging technologies in place. Diesel has a higher energy density as compare to Petrol, Diesel combusts by being compressed which ensures that most of the Diesel burns to turn the crank.
This means less Diesel is needed to achieve the power of a Petrol engine. Diesels also can achieve high gears at low revs which especially helps fuel consumption to be low and have high torque at low revolutions which means they can pull heavy loads.
Despite the situation being how it is right now there are several new innovative technologies being employed to improve fuel efficiency. Electric batteries are increasingly being employed in many cars, there are two types of hybrid systems being used in cars, the plug-in type and the one charged by the car.
The plug-in type means you can travel a predetermined distance depending on the battery size, and it offers great fuel efficiency. The battery charged by the car offers a hybrid system where the car uses the internal combustion unit and the battery, it offers good fuel efficiency.
Another innovative method being employed is when in traffic and the car is in Neutral the engine turns off, when the driver engages the gear and accelerates it turns on and drives. This is a simple method, but it helps save fuel especially for urban and city driving and saves on emissions.
Aerodynamics improvement and low rolling resistance tyres are very effective at reducing fuel consumption car manufacturers are improving air flow vents, underbody panels and use of deflectors.
I look forward to reading your comments about this article.
Author: Sam Ndegwa
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