Fuel efficiency is an important measure of a car’s performance. In simple terms, it is a measure of how effectively a car performs per a given unit of fuel. Improving fuel efficiency is always high on the agenda of car manufacturers and governments are also heavily invested in it. If cars have lower fuel efficiency, it means that the car will waste fuel as heat instead of going the distance. It will be expensive for the customer, so it is in the manufacturer’s interest to improve it as well.
For governments, especially those that have to import diesel and petroleum, this means that people will be spending a lot of money importing fuel. This is obviously not good for their trade balance. Another reason is that lower fuel efficiency for fossil fuel powered cars will mean more carbon emissions and hence more air pollution. So, governments are also trying to incentivize car manufacturers to increase fuel efficiency as much as possible.
Car Features that Affect Fuel Consumption
The shape and aerodynamics of a car body is a major contributing factor to how efficiently the vehicle will use fuel. The chemical energy in the fuel is not only used to drive the car, but also to cover other losses such as air resistance.
A car spends a lot of energy, and hence fuel, in overcoming air resistance. Hence, car manufacturers are continuously improving the aerodynamics of their car models. This is mostly done by streamlining the car body as much as possible.
Car body shapes that have sharp turns and edges will have to spend more effort in trying to overcome air resistance. More rounded, streamlined car bodies tend to be the most aerodynamically efficient. You will see this in nature as well, where most fish will have smooth elongated bodies to overcome drag easily. Air and water are both fluids, so the aerodynamic shapes behave in similar ways in overcoming resistance.
Aerodynamic research is a huge field of study in both the automotive and aviation industry. There is specialized, dedicated software for optimizing aerodynamic designs. The reason that a lot of resources are dedicated to aerodynamics is because a small change in the shape (in aviation, even dirt particles are enough) can have significant effects on overcoming air resistance and hence the fuel economy.
Aerodynamics is just one of many car features that will affect fuel consumption. Engine design also has a significant impact on fuel efficiency.
Other Factors that Increase Fuel Consumption and Efficiency
- Added cargo that can change the aerodynamic shape of the car will increase air resistance and hence fuel consumption. Not only does this increase air resistance, but it also adds weight which means the car expends more energy.
- Driving in cold weather regularly can increase fuel consumption
- Taking too many short drives. Engines work most efficiently when they have had time to warm up.
- Driving at higher speeds. Higher speeds generate more air resistance, so it will use up more fuel.
- Alignment issues in the tyre can reduce fuel efficiency. Also, higher pressures in the tyre prevent deformation and increases fuel efficiency.
- Problems with the fuel injectors can mean fuel is wasted from the start.
Technologies that Improve Fuel Efficiency
- Transmission types also effect fuel efficiency. Continuously variable transmission (CVT) will give a higher fuel efficiency as it enables the engine to run at optimum RPM.
- Reusing waste heat from the exhaust improves fuel efficiency
- Novel lightweight materials can reduce the rolling resistance of the vehicle.
- Cylinder shut-off mechanisms can increase fuel efficiency only running cylinder that are needed.
- Generally, hybrid vehicles have a higher fuel efficiency because an electric motor is used in conjunction with the engine. The petrol engine is used when it is really necessary. (More on this later).
Measuring Fuel Economy/ Fuel Efficiency
In transport, fuel economy is synonymous with fuel efficiency. Fuel economy, in simple terms, is measured by how much distance can be covered by the vehicle per given unit of fuel. Inversely, it can also be represented by how much fuel is required to cover a unit distance.
In countries that use the metric system, fuel economy is measured in terms of litres per 100 kilometres. These countries include most of Europe, Australia, China, New Zealand and some parts of Africa and Asia. In countries such as the US, UK and Canada, fuel economy is measured in terms of miles per gallon (MPG). In the Middle East, it is measured by distance per 20 litres of fuel. The higher these values are, the more fuel efficient the vehicle is.
How Hybrid Vehicles Have Changed the Game for Vehicle Fuel Efficiency
Are hybrid vehicles more fuel efficient than normal cars? To give a simple answer, yes, they are more fuel efficient. They are, in fact, the most fuel efficient of all vehicles. On average they have a fuel economy of 50-60 mpg whereas it is around 40 mpg for regular non-hybrid vehicles, saving you more money on gas.
Overall, hybrid vehicles contain an internal combustion engine, battery, electric motor and generator. Hybrid vehicles are more fuel efficient because they use a combination of an internal combustion engine (ICE) and an electric motor to deliver power. These two power units complement each other, because the electric motor can drive the vehicle at speeds that the ICE is not efficient at. Hence, you get the best of both worlds. This also means that the ICE can be smaller than in regular vehicles and can be switched off when the vehicle is in idle.
Requirement of Batteries
However, because hybrids rely on electric power they also require batteries that need to be charged. These batteries, along with the generator can add significant weight to the car which outweighs the space-saving benefit of a smaller ICE engine. So, even though hybrid vehicles are the most fuel efficient, they only win by a small margin. They are only around 20-30% more efficient than normal vehicles.
The savings of fuel costs as a result of the higher fuel efficiency also do not offset the higher cost of hybrids. It is estimated that over a 10-year period, you only save about $2,300.
But, the good news is that hybrid technology is continuously improving. It is a relatively new technology, so it is very likely that rapid technical innovation will drive down the prices and improve fuel efficiency even further.
Now that we know how hybrid technology improves fuel efficiency, we will take a look at the five most fuel-efficient hybrid cars.
Top 5 Most Fuel-Efficient Hybrid Cars
1. Hyundai Ioniq Hybrid
At an impressive mileage of 57 MPG, Hyundai’s 2018 Ioniq takes the cake for the most fuel-efficient car in the US. The Ioniq series has been the most fuel efficient, ever since it launched back in 2016. With a streamlined car body made of lightweight materials and a very powerful engine that delivers an impressive thermal efficiency of 40%.
It also wins for being the best bang for your buck at just over $23,000. Hence, it beats out its biggest rival, the Toyota Prius in terms of cost and fuel efficiency. The Ioniq series is available as full-electric and plug-in hybrid models.
2. Toyota Prius
A name that has always been renowned in the hybrid world, the Toyota Prius takes the second place with a mileage of 53 MPG (highway) and with no plug-in option. This car is a four-doored hatchback that has room for five people. It is also reasonably priced, at $24,370 but not enough to beat Hyundai’s Ioniq.
The main updates to this model from the previous Prius cars is that it has more advanced safety technology with features such as blind-spot monitoring.
3. Toyota Camry Hybrid
The combined city-highway mileage for the 2018 Toyota Camry is 53 MPG. It is slightly pricey at over $28,000. This model revamps the Sedan to have a fuel economy rivalling the Prius. However, certain models such as XLE have lower fuel economy at around 47 MPG.
It also has good safety technology such as the inclusion of the Pre-Collision System (PCS) which alerts the driver of a potential collision and also has Pedestrian Detection system.
4. Kia Niro
The best fuel economy is in the FE version of the Kia Niro series of hybrid hatchbacks. The highest fuel economy is 49 MPG (highway) for the FE models. The other models have slightly lower mileages ranging from 40-46 MPG (highway).
The 2018 Kia Niro also comes at a modest price of $24,280 which is more economical than the Camry.
5. Chevrolet Malibu Hybrid
Another sedan-turned-hybrid from Chevrolet comes in at the 5th spot with a highway MPG of 43. It is quite expensive at $28 795 comparable to Toyota’s Camry. However, it has a lead of 10 MPG over the Chevrolet Hybrid. It also has a more spacious cabin than the Chevy Hybrid. But, in general, the Malibu is a decent mid-size car with great fuel economy.