Fuel Economy is an important measure of a car’s performance. It shows how effectively a car utilizes the fuel you give. It is also a reflection of the quality of the internal components and mechanisms of a car. A good fuel economy means a car’s vital components like the engine are of a good quality and doesn’t waste fuel.
It’s a great way to compare cars with each other and is frequently used on comparison and review websites to gauge the performance of new car models on the market. You want a car with a good fuel economy because this would mean that less fuel is wasted as forms like heat or friction.
There are many reasons why buying a car with good fuel economy is important:
Quality and Performance
As mentioned before, fuel economy is a reflection of the quality of the car’s key components like the engine. If the engine is of poor quality or in a bad condition, the car would have a poor fuel economy.
Reflects on Environmental Impact
A poor fuel economy means that to meet a certain performance criteria such as speed or distance, the car will use more fuel. More fuel means more emissions of greenhouse gases. As our world faces ever-mounting pressure to tackle climate change and vehicle pollution is a major contributor, improving fuel economy is a top priority for consumers and car manufacturers alike.
Cost of Fuel
A poor fuel economy means that more fuel is wasted to do a certain task. This is not only bad on the emissions front, but it’s terrible for your budget. Especially considering that gasoline prices are usually expensive and highly volatile, a car with a bad fuel economy is the last thing you need. Hybrid cars provide an instant way to save money on gas spend, especially those with daily long commutes.
What Exactly Is Fuel Economy?
In simple terms, fuel economy is a measure of the maximum distance (in miles or km) that can be travelled by a car per gallon of fuel. Don’t confuse this with range, which is the maximum distance that one can travel on a full gas tank.
Sometimes however, the formula is also reversible to measure the volume of fuel it takes to complete a certain distance. Either way, it gives a measure of how effectively a car uses its fuel.
Distance Travelled per Fixed Unit Volume of Fuel
In the US, the measure for fuel economy the distance per unit fuel, in this case miles per gallon (MPG).
Other countries in Africa and Asia also use distance per unit fuel but measures it in kilometres per litre (km/L). In Arab countries, the fuel economy measurement is in kilometres per 20 litres of fuel, km/20L.
Fuel Volume Consumed per Unit Distance
In European countries, China, Australia and New Zealand, fuel economy usually measures in the volume of fuel per fixed unit distance. So, this would be in litres per km or L/km.
The UK, Ireland and Canada follow both conventions and you will find cars measured in MPG as well as L/km.
How to Find Fuel Economy
You can find out the fuel economy of a car as they are usually officially listed by the car manufacturers. In the US, there is a database called fueleconomy.gov where you can find out the fuel economy for a certain car model and year as rated by the EPA (Environmental Protection Agency).
Alternatively, if you car isn’t new, you can do a test of your own and see how much fuel is consumed for a known distance. This could be a useful guide to see any potential problems with the engine or the car.
Interpreting Fuel Economy Figures
In official fuel economy listings and databases for regular gasoline and hybrid vehicles, you will often see three types of MPG ratings:
- City: This is the fuel economy that’s measured under driving conditions you will often encounter in a city, such as traffic. So, this would be short distances with periodic stopping and deceleration.
- Highway: This is the fuel economy measured on a highway or long road with little traffic. The acceleration is continuous and not sporadic like in the city.
- Combined: This is the average of the city and highway figures.
Of course, none of these figures take into consideration, a driver’s individual driving style or specific driving conditions in the area you live in.
Fuel Economy for Hybrid Vehicles
To understand how fuel economy works in hybrid vehicles, we need to know briefly how they work. There are two types of hybrid vehicles: Conventional hybrids and Plug-In hybrids.
Regardless of the type, all hybrids use a combination of electric power and gasoline to propel the car. So, they have an electric motor as well as an internal combustion engine, along with a gas tank and a battery pack to store the energy. They all employ regenerative braking. A technology that allows the car to capture the kinetic energy. Energy which is lost in traditional vehicles as heat.
Conventional Hybrids Vs Plug-In Hybrids
Conventional hybrid batteries are not rechargeable by an external power source, they only receive charge during regenerative braking. You can charge Plug-In hybrid batteries with an external electric power source such as a standard electric outlet or an EVSE (Electric Vehicle Supply Equipment).
Hence, conventional hybrids only measure the fuel economy of the gasoline. The plug-in hybrids have to combine the fuel economy of both the electricity and the gasoline.
Electricity can’t be measured in gallons, so for plug-in hybrids, fuel economy is measured in something called ‘miles per gallon equivalent, or MPGe. Here, they measure the amount of electricity that has the same energy as a gallon of gasoline. For calculations, it is assumed by the EPA that 33.7 kWh of electricity is equal to one gallon of gasoline.
For simplicity, it is assumed that the car operates only on the battery and that the engine is engaged only when the battery is depleted. It doesn’t consider the car operating on a mix of electric power and gasoline at the same time. The formula for MPGe is:
MPEg= (s1+s2)/ (s1*EE/3370 +s2/MPG)
MPGe= Miles per Gallon equivalent
S1= total range on battery only
S2= total range on gasoline only
EE= Energy Efficiency of battery in kWh/100 miles
MPG= Fuel Economy of Plug-In operating on gasoline only
MPGe of popular hybrid car models
Chevrolet Volt 2019: 106 MPGe, 42 MPG (combined city/highway when operating on regular gas)
Toyota Prius Prime 2019 : 133 MPGe, 54 MPG
Hyundai Ioniq Plug-In Hybrid 2019 : 119 MPGe, 52 MPG
Honda Clarity Plug-In Hybrid 2019 : 110 MPGe, 42 MPG
Conventional Hybrids-
Hyundai Ioniq 2019: 55 MPG (combined city highway)
Toyota Prius 2019 : 52 MPG (combined)
Toyota Prius AWD 2019 : 50 MPG (combined)2019 Toyota Prius C: 46 MPG (combined)
