Are Newer Cars More Fuel-Efficient Than Older Cars?

Whether it’s to reduce harmful CO2 emissions or to save money at the pump, fuel efficiency is something that many Kiwis value when looking for a new car. As you may expect, a car made 10 to 15 years ago will probably not get the same litres per 100 kilometres as a similar new car today. However, what is surprising is that this has less to do with how old the car is and more to do with the way a newer car is made.

From lightweight and strong materials, to refined aerodynamics and improved engine technology, automakers like Suzuki, are getting better and better at optimizing fuel efficiency in the vehicles they make.

Let’s take a look at what fuel efficiency is and what makes modern cars more economical, so you can decide if it’s time to trade-in your old car for a fuel-efficient one.

Engine efficiencies

Over a century ago, Karl Benz designed and built the world's first practical automobile, which was powered by an internal combustion engine. This invention was the beginning of the use of petrol engines in vehicles worldwide. What’s interesting is that the basic principles of the combustion engine remain the same today.

To understand fuel efficiency improvements, here are the basics of how a petrol-powered engine works. Combustion is the chemical process of burning air and fuel. When the gas and oxygen ignites and explodes inside a cylinder, this is what moves the engine’s pistons up and down. The crankshaft which is connected to the pistons then rotates, creating the energy in the transmission to move the car.

Aside from older cars being heavier and engines being larger in size, their combustion process was incredibly inefficient. Old engines burnt a lot of fuel, only to convert about 15% of it into the mechanical energy used to move a car. The rest of the energy was lost by heat, friction, idling and other parasitic losses (refers to energy lost due to inefficiencies in a system).

Fast-forward to today; some of the modern engine features that carmakers have developed to get as much energy as they can from fuel include direct injection technology, the ability to increase compression ratio and teaming up with improved transmissions.

Direct-injection technology, in Suzuki’s BoosterJet engines for example, does not pre-mix the fuel and air before reaching the cylinder, like older engines. Instead, the right amount of fuel is directly injected into the cylinders to optimise combustion, providing up to a 12% improvement in fuel efficiency.

Turbochargers like those in the S-Cross Turbo use the energy from the compressed gases from a car's exhaust to increase power output without having to increase the size of the engine, thereby increasing efficiency further.

Variable valve timing helps control the flow of fuel and air into, and the flow of exhaust out of, cylinders in the engine. This technology regulates the valve timing depending on the type of the work the engine is doing so it will use less fuel and work smarter. A great example of this is the Suzuki Swift.

These technologies often combine with an increased compression ratio (the amount of air-gas mixture compressed in the cylinder). The higher the compression ratio, the more work an engine gets out of the same amount of fuel, which means the engine can be smaller and produce more power efficiently.

Alongside engine improvements, new cars have other modernised high tech components such as more gears or Continuously Variable Transmissions (CVT). Higher gears or in the case of CVTs (infinite number of gear ratios) help the engine transmit power to its wheels as efficiently as possible.

Aerodynamic efficiency

Another aspect of modern car design that has changed over time is the emphasis on aerodynamics to improve fuel efficiency. Aerodynamic drag is particularly relevant when driving on open roads as it accounts for more than half of the fuel you’re using, or even more. The faster you go, the more fuel you use to push your car through the air.

Car designers and engineers now spend more time not only making a vehicle look good, but developing a shape that provides as little resistance as possible as it travels through the air. The smoother the airflow, the lower the drag there is, the less fuel you burn at a certain speed.

It’s also more cost-effective for automakers to improve efficiency with aerodynamics than through weight saving or engine technologies.

Here are a few of the things in new cars that have improved airflow:

• Smooth, rounded edges at the front of the vehicle as sharp corners and edges increase turbulence and drag

• Grill openings optimised to reduce turbulence both outside the car and under the hood

• Carefully shaped outside mirrors and mounts

• Aerodynamically optimized water channels on A-pillars

• Side skirts to control airflow under the car

• Rear spoilers to reduce lift

• Carefully calculated rear window angles

• Rear diffuser to control air coming off the vehicle underside

• Belly pans to smooth airflow under the vehicle

Manufacturing efficiency

As technology and our understanding of metals have evolved, some manufacturers such as Suzuki have developed cars to become much lighter and safer.

Older vehicles were made of thicker metals such as steel and cast iron. This made them very heavy, although not necessarily stronger.

While steel is still a main component of car construction today, especially in body structure and outer panels, the introduction of high tensile steel and other alloys has meant better strength and durability. Other lighter materials such as carbon fibre, aluminium, copper, magnesium, fibreglass, plastics and even ceramic materials have been introduced into car manufacturing to reduce weight and improve fuel efficiency.

As well as core materials, advancements in metal forming processes such as bending, extruding and stamping, has meant vehicle parts can be formed into strong yet thinner and subsequently lighter parts for assembly.

Hybrid efficiency

As countries work together to become more environmentally sustainable, CO2 emission standards are challenging automakers to introduce other technology that is more climate-friendly. Electricity and hydrogen are some of the alternative sources of energy which are having a flow on effect on improving fuel efficiency in cars.

Hybrid vehicles that use both electricity and petrol to power their engines are becoming more commonly available in New Zealand. As infrastructure improves and the price becomes more affordable, they are a logical next step to consider when buying a new car that is fuel efficient.

What is fuel efficiency?

Fuel efficiency is how far your car can travel on a certain amount of fuel. The most common measure is litres per 100 km (litres/100 km) which is the number of litres of petrol or diesel a car needs to travel 100 km (often referred to as "fuel economy").

Generally, the lower the number of litres/100km stated, the better the fuel economy. Anything that is listed as less than 6 litres/100 km (NEDC combined result) or more than 16.5 km per litre is considered to be pretty good.

Driving a fuel efficient car comes with several perks, including:

• Saving fuel costs - You’re probably well aware that the price of gas is one of the major issues that drivers face. By driving more economical cars, you will not only save on fuel, you can spend the money you’ve saved on your next holiday or that special something you’ve been eyeing up.

• Reducing carbon footprint - Driving a fuel-efficient car is by far one of the best ways to fight climate change. This is because fuel-efficient cars emit less CO2 emissions.

Driving fuel efficiently also helps reduce your fuel consumption:

• Drive steadily - Avoid heavy braking and accelerating by smoothing out your driving.

• Remove any excess weight - Be mindful of the load you are carrying, as the heavier your car is the more gas you use.

• Maintain your car – By regularly servicing your vehicle, using the right fuel and keeping your tyres pumped up to the right air pressure, you keep your car running at its fuel efficient best.

Every year, the auto industry continues to adapt their designs and refine the process and materials to produce vehicles that are lighter, safer and more economical. As technology changes, holding onto your older car may not be as beneficial as investing in an affordable and fuel-efficient new car.

If you are looking to buy a more fuel-efficient car, our Guide to Buying a New Car will give you the insights you need to take the next step!