Car fuel economy: What it is and why it matters

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In a Nutshell

Your car’s fuel economy — how far your vehicle can go using a specific amount of fuel — can have a real impact on your expenses. Choosing a vehicle with good fuel economy, or taking steps to boost the fuel economy of your current vehicle, just might save you money at the gas pump.

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Car fuel economy is directly related to miles per gallon, or mpg. The higher its mpg, the better your car’s fuel economy.

Read on to learn what fuel economy is and how it’s calculated. We’ll offer some guidance you can use when shopping for a car as well as how you could help improve your current car’s fuel economy.



How does fuel economy work?

Fuel economy refers to the number of miles a car can travel using a specific amount of fuel. It’s measured in miles per gallon or miles per gallon gasoline equivalent (or MPGe) for electric vehicles. The more miles per gallon a car gets, the farther it can go on a tank of gas and the better its fuel economy.

You may have heard car fuel efficiency and car fuel economy used interchangeably. But car fuel efficiency is actually different — it refers to the amount of fuel used to power a car rather than indicating how far the fuel will take the vehicle.

How is fuel economy calculated?

Fuel economy is measured by automakers through a series of tests conducted in a laboratory and then reported to the U.S. Environmental Protection Agency. The EPA reviews the test results and confirms a percentage of those results through its own tests.

The EPA offers fuel economy estimates for many of the vehicles currently on the road. For EPA estimates, head over to fueleconomy.gov.

How do I calculate my car’s mpg during a trip?

First, you’ll need to log the miles you drive and how much fuel you used to get to your destination. Dividing the miles you traveled by the number of gallons you used will give you a reading of your car’s mpg for that particular trip.

What is good fuel economy?

The EPA’s 2020 list of the best-fuel-economy vehicles features models that all have a combined mpg of at least 22 mpg — but keep in mind that what’s considered good fuel economy can vary by the type of vehicle. For example, minivans (coming in at that 22mg) and pickup trucks may have lower mpg across the board than a subcompact car.

If you’re shopping for a fuel-efficient car, it’s important to consider each vehicle’s EPA-rated fuel economy. At fueleconomy.gov, you’ll find fuel economy data for cars from the current model year all the way back to 1984. And if you’re already checking out cars and SUVs at the auto dealership, you’ll find fuel economy information reflected on the vehicle’s window sticker, which has other useful data about the car, like fuel economy rating and estimated annual fuel cost.

Which cars have the best fuel economy?

When it comes to gas-powered vehicles, EPA data reveals that the cars with the best fuel economy in 2020 are often those with hybrid powertrains. According to the EPA, hybrids like the Toyota Prius Eco, Toyota Corolla Hybrid, Kia Niro FE and Hyundai Ioniq Blue are top picks in their segments for fuel economy.

Among electric cars, EPA data shows that some of the most-efficient choices include the Tesla Model S Long Range and Model 3 Standard Range Plus, Chevrolet Bolt and Volkswagen e-Golf. Some plug-in hybrid vehicles — the BMW I8 Roadster and Karma Revero GT — also made the list. Adding to your potential savings, certain electric vehicles are eligible for tax credits of up to $7,500.

Keep in mind that in some cases hybrids and electric cars may cost more to buy than their gas-only equivalents, but they just might end up saving you money down the line when it comes to the total cost of ownership.

According to the EPA, these fuel-cost savings can be significant. The agency gives this example: A vehicle that gets 30 mpg will save you $663 in annual fuel costs compared to a car that gets 20 mpg. This estimate assumes that you drive 15,000 miles each year using fuel that costs $2.65 per gallon. With those numbers over five years, the fuel savings add up to $3,313.

Tips for optimizing your car’s fuel economy

It’s important to remember that a vehicle’s EPA-rated mileage is an estimate based on a standardized test. Your real-world mileage may vary depending on different factors, like your car’s overall maintenance schedule and your driving habits. Weather, particularly frigid temperatures, can hurt fuel economy. According to the EPA, temperatures below 20 degrees Fahrenheit can reduce a vehicle’s fuel economy by as much as 34% in some circumstances.

With those points in mind, here are some tips for optimizing your car’s fuel economy.

Avoid speeding and aggressive driving

Speeding and aggressive driving can take a toll on your car’s fuel economy. Rapid acceleration and heavy braking can lower your fuel economy by as much as 30% at highway speeds and 40% in stop-and-go traffic, according to a 2017 study conducted by the Department of Energy’s Oak Ridge National Laboratory. And gas mileage usually decreases pretty quickly when vehicles travel at speeds over 50 mph.

Get rid of unnecessary weight

Many of us haul around items we don’t need in the trunk of our cars. Avoid traveling with items that aren’t necessary, since the excess weight could compromise your car’s fuel economy. An extra 100 pounds in your vehicle might reduce fuel economy by 1%, according to a 2008 study cited by the EPA.

Avoid using roof-mounted cargo boxes

A roof-mounted cargo box can add utility, but at a cost. These boxes increase wind resistance, which, according to a 2014 study cited by the EPA, can reduce fuel efficiency by as much as 25% when traveling at interstate speeds.

Keep your tires properly inflated

In addition to creating a safety hazard, underinflated tires can reduce gas mileage by about 0.2% for every 1 pound per square inch (or psi) drop in the average pressure of all tires, according to a 2012 study conducted by the National Highway Traffic Safety Administration. But keeping your tires inflated according to manufacturer specifications may improve your gas mileage by up to 3%.

Be diligent about keeping your car’s engine maintained

A problem with your car’s engine could also affect fuel economy. A serious problem, like a compromised oxygen sensor, could drop mpg by as much as 40%, according to a 2001 study conducted by Energy and Environmental Analysis Inc. So it’s a good idea to get regular tune-ups to help avoid paying more at the pump.

How much does an oil change cost?

What’s next?

If you’re in the market for a new or used car, consult the fueleconomy.gov site to see how your choices stack up when it comes to fuel economy. And if you’re interested in optimizing the fuel economy of your current car, start by clearing unnecessary items from the trunk or cargo area, and checking the tires to make sure they’re properly inflated.


About the author: Warren Clarke is a writer whose work has been published by Edmunds.com and the New York Daily News. He enjoys providing readers with information that can make their lives happier and mor… Read more.