What Is Fuel Efficiency?

Fuel efficiency is how far a vehicle can travel on one gallon of gas. It can be influenced by several factors, including how the vehicle is driven and maintained.


For example, frequent braking and acceleration can eat up your fuel. Likewise, idling your engine wastes fuel and produces more pollution.

Lighter Vehicles

A vehicle’s weight determines how much energy it takes to get moving. The heavier the vehicle, the more energy it needs to move forward; extra weight also increases a vehicle’s rolling resistance, which resists the force of the tires against the road and adds to fuel consumption.

Consequently, the best way to improve a car’s fuel economy is to make it lighter. Strict fuel-economy standards and new materials such as aluminum and composites are helping to make cars lighter. A useful industry guideline is that for every 10% of a vehicle’s weight reduction, its fuel economy can be improved by 6-8%.

One of the most difficult things about achieving better fuel efficiency is that reducing vehicle weight often comes at the expense of other desirable features such as safety, comfort and performance. But engineers can compensate for these trade-offs with improvements in powertrain and transmission efficiency and by switching to lighter components.

In addition to improving a vehicle’s fuel economy, going lighter can help it accelerate faster and handle corners more effectively. This is because a lighter vehicle has less inertia, and its centre of gravity is lower.

As a result, vehicles that are lighter tend to have safer accident outcomes. Research by the National Bureau of Economic Analysis found that as the average weight of vehicles has dropped, there have been fewer accidents between large and small vehicles—which are the most deadly of all vehicle-on-vehicle crashes.

New Fuel Sources

The type of fuel a vehicle uses directly affects the amount of pollution it creates. Many alternative fuels and vehicles have been developed that reduce oil consumption or limit greenhouse gas emissions. These new fuels may be used in vehicles without modification or be blended with traditional gasoline to increase the vehicle’s efficiency. Alternative fuels include natural gas, ethanol and biodiesel.

These alternative fuels can be locally sourced, reinforcing a domestic supply chain and reducing the influence of global energy markets on US prices. They also help fleet operators reduce their dependence on fossil fuels by using a blend of different fuel sources.

Ethanol, an alcohol produced by fermenting starchy vegetables and plants, is a popular renewable fuel that can be used in conventional vehicles. Biodiesel is made from animal fats and vegetable oils, often recycled from restaurant waste, which can be used in diesel engines. Propane, a readily available gaseous fuel, is a cleaner option than either petroleum or diesel fuels and limits the production of harmful exhaust pollutants such as nitrogen oxide.

Research is continuing into finding suitable crops to make a more sustainable source of biofuel as well as improving the yields from current oil-producing plants. These efforts, along with other advances to improve advanced engine technology and reduce parasitic losses like drag and idling, will help further enhance the fuel efficiency of motor vehicles.

Reducing Motor Vehicle Weight

Fuel efficiency is an important part of car ownership because it reduces the amount of energy that’s needed to travel a certain distance. It also cuts down on air pollution, promoting a cleaner environment for everyone. Various strategies are employed to improve fuel efficiency, including reducing vehicle weight and using alternative power sources.

Boosting the braking performance of a vehicle is another strategy to increase its fuel efficiency. This helps drivers slow down their vehicles more gradually, which allows the engine to shut off sooner and saves on fuel use. In addition, it requires less force from the brakes to bring the vehicle to a stop, which extends their lifespan.

Reducing motor vehicle weight also offers several other benefits, such as improved acceleration and handling. The ability to reduce vehicle weight can be accomplished through a variety of means, such as removing unnecessary items and choosing lightweight accessories. However, it’s important not to make modifications that compromise the safety of a vehicle, especially if they are designed for racing or track use.

The terms fuel efficiency and mileage are sometimes used interchangeably, although they differ slightly. Mileage is the standard unit of measurement in the United States and the UK, while countries using the metric system express this measure as kilometers per liter or litres per 100 kilometers (L/100 km). Fuel efficiency is a more specific term that describes how well a vehicle uses fuel.

All-Electric Cars

As the EV market grows, more models are entering the marketplace that offer class-leading efficiency. For instance, the 2022 Kia EV6 GT Line has an EPA-estimated combined city/highway MPGe of 83 and uses 24 kWh to travel 100 miles. In comparison, a Porsche Taycan GTS with its 93.4-kWh battery pack provides 246 miles of range and has an EPA MPGe rating of 100.

Those figures are for electric-only driving, but plug-in hybrid electric vehicles (PHEVs) also typically have a gasoline MPGe rating on their EPA fuel efficiency labels when they run on gasoline only. Those two ratings allow you to compare their energy-efficiency and range figures against those of conventional gasoline cars when they are using gas.

In addition to offering more efficient motoring, EVs produce no tailpipe emissions that contribute to air pollution. And they’re often more cost-efficient than conventional gasoline cars to operate, particularly if drivers take advantage of off-peak electricity rates to charge their batteries at home.

As for maintenance costs, EVs usually require less work than traditional internal-combustion vehicles because they have fewer parts and fluids. They can even go longer between oil changes, though they do still need routine maintenance like tire rotation and wiper blade replacement. And because they use regenerative braking to recapture some of the energy used when you brake, they tend to be two to three times more efficient than conventional engines.