GreenCars 101

Fuel-Efficient Vehicle Overview

Dave Nichols
Jul 2023
What defines a fuel-efficient car? From speed and weight, to engine efficiency and aerodynamics, a number of factors contribute to a vehicle's ability to get great MPG efficiency. Let's take a look at each right here on GreenCars.
Car driving up a mountain overlooking a scenic forest

What Makes a Car Fuel Efficient?

Obviously, a car that gets great gas mileage can be called fuel efficient, but there is a lot more to it than that. The Environmental Protection Agency (EPA) has its own fuel economy rating for every car you can buy today. They put each vehicle through a variety of tests to determine how many miles per gallon it gets on the highway, in city driving, and combined driving. This combined mileage is the average amount of miles per gallon for most drivers. Fuel efficient vehicles combine a number of different qualities to earn the right to be called fuel efficient. These include the following features:

Aerodynamic car with red wave over top ofcar


A fuel-efficient car must slice through the wind. That’s why most hybrids, plug-in hybrids, and all-electric vehicles are more bullet shaped than say, a standard pickup truck. It all has to do with how air flows around the car. You see, air produces a lot of force against a vehicle when it is pushing through the air at 60 miles per hour or more. Aerodynamic design incorporates the use of wind tunnels to test and track how wind efficient a vehicle is. Air flowing around a blunt design will cause drag and slow the car down. Automakers spend a great deal of time and money to create car body designs that flow through the wind effortlessly with the least amount of gas or electricity possible.

close up of speedometer

Fuel-Efficient Vehicles: Speed

The speed which you are driving affects fuel efficiency. You can have a car that gets great fuel efficiency numbers but if you’re a lead foot, you will use up more fuel. The key is to drive consistently at even speeds without putting the pedal to the metal for quick launches. Drivers who are constantly adjusting the speed they are traveling, will use up more fuel. The less you accelerate, the less fuel you burn, it is as simple as that. That’s why using your cruise control will save you money at the pump. It keeps your speed consistent.

Green lit button reading, "Hybrid Power"

Engine Efficiency

Automakers spend vast amounts of money to design engines that work at optimum efficiency to get you better mileage figures. This has to do with many factors include the engine size, the number of cylinders, and the overall amount of power the engine produces as well as constantly improving technology. Generally speaking, a properly tuned four-cylinder engine will provide much better fuel efficiency than a gas-guzzling V8. But modern V8s even shut down some of the cylinders when they are not needed for better fuel economy

Silver Car on the road


One of the things that impacts fuel efficiency the most is the weight and size of the vehicle. Bigger vehicles are usually heavier and burn more gas. The bigger and heavier the vehicle, the more energy it takes to move it. This is especially true of vehicles such as pickup trucks that are meant to haul or tow heavy loads. The same is true of family-sized SUVs. Big, bulky vehicles tend to have lower fuel efficiency ratings from the EPA.

The use of hybrid (HEV) and plug-in hybrid electric (PHEV) technology is improving fuel efficiency by adding an electric motor and battery pack for better mileage and offer an efficient blend of gas and electric drivetrains.

Car parked in Electric Vehicle Only charging spot

Today’s Fuel-Efficient Cars

Many of the most fuel-efficient vehicles today are also under $30,000 and get over 30 miles to the gallon of gas. Every car has an EPA rating for miles per gallon. However, the type of fuel your car requires also plays into the equation.  Today’s most fuel-efficient vehicles are zero emission vehicles such as all-electric cars (BEV). According to the California Air resources Board (CARB), fuel efficient vehicles are defined as vehicles that have achieved a minimum green score of 40 on the American Council of Energy Efficiency Economy (ACEEE) rating guide.

Front view of a Tesla Model 3 driving through canyon roads

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