8 Factors Affecting Mechanical Efficiency of a Car

Daniel Mwangi
10 Min Read
Image of gas station

What is fuel?

Mechanical efficiency is every vehicle owner’s concern, especially when the price of fuel is at an all-time high. Fuel is any combustible substance that produces energy when it ignites. The main forms of fuel in automobiles are diesel and petrol. Petrol is the same as gasoline in some regions. Petroleum or fossil diesel is the most common type of diesel. Synthetic diesel, biodiesel, and hydrogenated oils and fats are other types of diesel.

Since we can neither create nor destroy energy, we can only convert from one form to another. Internal combustion engines perform these power conversion processes to induce motion for the vehicles. The potential chemical energy in the fuel ignites to produce heat energy. Heat energy converts to kinetic energy through linear motion in pistons. Pistons drive the crankshaft and drive chains to produce mechanical energy, which in turn drives the wheels.

It is in these power conversion processes that the factors affecting fuel consumption are at work to dictate either a low or a better fuel economy.

What is Fuel Economy? 

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Fuel economy in Europe and other metric regions is the amount of fuel a vehicle uses to cover a distance of 100 kilometres. In the US, the measurement is in miles per gallon. If a vehicle consumes more litres for a 100-kilometre distance or covers fewer miles per gallon of fuel, then that is called low fuel economy.

There are several factors affecting fuel consumption in vehicles, thereby contributing to either a low or a better fuel economy. In this article, we will look at some of the major contributors to low fuel economy and also touch on tips to help you achieve better fuel consumption for your vehicle.

Why is fuel economy important?

Fuel economy is an integral element in automobile economics. How well or badly your vehicle consumes fuel dictates the total cost of running your vehicle. Fuels are not cheap by any standards, hence the fuel consumption of your vehicle is directly proportional to the financial dent in your wallet.

The other aspect is the environmental impact. Vehicles with better fuel economy release fewer pollutants into the atmosphere. Less efficient cars are detrimental to the environment.

What is fuel efficiency?

Fuel efficiency and fuel economy are closely related and are often confused to mean the same, but they have distinct and separate meanings. While fuel economy is consuming the lowest amount of fuel within a set distance, fuel efficiency is getting the best output for the amount of fuel input. 

If a vehicle travels more miles per gallon of fuel (MPG), then we say that the engine is fuel efficient. In the metric system, if a car uses less fuel for a certain distance (L/KM), the engine is fuel efficient.

What are the 8 factors affecting mechanical efficiency in vehicles?

1. Engine efficiency

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This is how efficiently an engine is able to perform the energy conversion processes with little energy wastage. It starts with the fuel and oxygen mixture at the inlet manifold, the actual combustion, and the transmission of energy to the drive chains.

A well-maintained engine, correctly tuned, and devoid of leaks ensures a smooth conversion of energy wastage. The correct air-to-fuel mixture allows for optimal engine performance and efficiency.

2. Aerodynamics

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The shape of a vehicle and ground clearance are some of the factors that affect the vehicle’s aerodynamics. Since air is generally considered fluid, automobiles are deliberately designed to minimize air drag. How easily air flows around a moving vehicle determines how much energy the vehicle requires to drive against it. 

A vehicle that is well-designed to exert minimum air drag, uses less energy to drive against air. This in turn means less fuel consumption.

Air drag is mainly due to three factors;

  • Frontal pressure, or the effort of a vehicle pushing through the air.
  • Rear vacuum or air trying to fill the space left by the vehicle.
  • Boundary layer, friction between air and the moving vehicle.

3. Vehicle weight

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Heavier vehicles require more energy to start and keep moving because they have more inertia and rolling resistance. Let us admit that there is nothing much you can do about the car’s actual weight unless you want to cut off part of the vehicle’s body.

But, you can offload unnecessary baggage in your vehicle, such as tools in your box that you may never use. Some people even carry replaced parts in their car boots. Just a few kilos of unwanted luggage can make a huge difference by getting the strain off your car’s engine and toning down on fuel consumption.

4. Tyre pressure

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Properly and correctly inflated tyres are another major determinant in fuel consumption. Maintaining tyre pressure at the recommended levels can improve your car’s fuel economy by up to 3%. 

Still on tyres, the size is also a big factor. Larger tyres are heavier and have a higher rolling resistance, hence lowering the vehicle’s fuel economy.

Also, remember to fit tyres that have a tyre tread pattern that is compatible with the terrain you are driving on, and the weather conditions.

5. Cold weather

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Mechanical efficiency can be substantially affected by cold weather through several factors;

  • Air drag is higher because the car is actually pushing through colder air, which is denser. 
  • The car engine takes longer to reach the optimum temperatures, which are required for good fuel efficiency.
  • The time it takes to warm up the engine before a trip starts consumes fuel but with zero returns on mileage.
  • Increased friction due to cold transmission fluids and engine oil means more energy is required, which in turn translates to more fuel consumption.
  • Cold weather reduces battery performance, hence putting a strain on the alternator. This strain is transferred to the engine and affects consumption.
  • The AC system is constantly in use to warm the car’s interior and to defrost, which strains the engine and lowers fuel economy.
  • There is more slippage on slick roads, and increased rolling resistance, which ultimately reduces fuel economy.

6. Driving habits

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Fuel consumption is largely dependent on how you drive your car. Some of the driving styles that increase consumption, and lower the car’s fuel economy are;

  • Rapid acceleration. Learn slow and smooth acceleration, then shift to higher gears as fast as practically possible.
  • Harsh braking. Anticipate the traffic flow ahead, so you can release the accelerator for engine braking.
  • Erratic speeds. Maintain steady speeds in place of intermittent speed dips and sudden accelerations.
  • Speeding. Keep your speeds within the specified optimum level for each car brand. Consumption significantly increases once you cross this mark.
  • Idling. Avoid unnecessary engine idling because it gives you nil returns for the car’s fuel consumption. Switch off the engine unless you are in traffic.

7. Transmission

Transmission dictates how much of the kinetic energy is transferred to the drive chains. If the transmission system is faulty then there will be losses in energy which in turn to a low fuel economy.

Some of the issues that contribute to poor transmission are;

  • Low levels of transmission fluids.
  • Worn-out parts, such as clutch plates and gears.
  • Wrong or delayed gear shifts, especially in manual vehicles.
  • Leaks in the transmission system.
  • Clutch-riding in manual vehicles.

8Mechanical efficiency

This entails all the parts around the drive chains, which use up the mechanical energy to provide mobility for your vehicle. Take great care by checking, servicing, and replacing these parts and systems;

  • Brake systems, such as brake pads, shoes, and brake fluids.
  • Constant velocity joints.
  • Tie-rods and tie-rod ends.
  • Ball joints.
  • Clutch plates, pressure plates, and bearings.
  • Wheel alignment and balancing.
  • Rear axle
  • Steering system

Only 8 Factors Affecting Mechanical Efficiency?

There are many factors affecting fuel consumption in automobiles. This article was not exhaustive on all those factors, but TechAuto Junction picked the ones that have a significant effect on fuel economy.

Your comments, additions, and corrections will be highly appreciated as we look to get the best value for money out of our automobiles.

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