Back To Blog
Key Takeaways
-
Reducing aerodynamic drag boosts fuel efficiency and performance. Even small improvements can deliver substantial annual savings, with streamlined trucks achieving up to 11% better fuel economy, reduced engine strain and improved handling.
-
Both tractor and trailer upgrades can cut drag. Add-ons like roof fairings, cab extenders, chassis skirts, side skirts and gap reducers improve airflow, while low-rolling-resistance tires, wheel covers and vented mudflaps help optimize efficiency.
-
Maintenance and cleanliness matter for aerodynamics. Securing panels, repairing damaged fairings and keeping the truck clean prevent unnecessary drag and maintain peak airflow performance.
Whether you're a fleet owner, an owner-operator or just someone considering stepping into your first rig, there’s one area of performance you don’t want to overlook: aerodynamics. Lowering aerodynamic drag directly improves fuel efficiency, and when you’re logging hundreds of miles a day, fuel savings add up. Fast.
Whether you drive long haul or regionally, here’s how you can fine-tune your truck’s aerodynamic profile and see real returns on the road.
Why Aerodynamics Matter for Semi Trucks
Air is invisible, but it’s one of the biggest forces working against your truck at highway speed. Once you reach 50 mph, aerodynamic drag begins to impact your truck's fuel consumption significantly. The U.S. Environmental Protection Agency (EPA) notes that semi trucks can spend a significant portion of their fuel energy fighting wind resistance at highway speeds. Reducing drag by even a small percentage can result in substantial annual savings.
For owner-operators or fleet owners, improving truck aerodynamics can mean the difference between profit and overhead. In fact, the EPA estimates that streamlined semi tractors paired with aerodynamic trailers can achieve up to an 11% increase in fuel economy, saving 1,651 gallons of fuel over the year (or $6,282* at today’s diesel prices).
More than fuel savings, better aerodynamics can also reduce engine strain, improve handling in crosswinds and cut down on wear to drivetrain components. All of that contributes to your truck’s longevity.
*As of July 30, 2025
Understanding the Basics: How Does Aerodynamics Work?
Aerodynamics is all about managing airflow. When your truck moves, it pushes air out of the way. That resistance creates drag. The more irregular, boxy or disrupted your truck’s exterior is, the harder your engine has to work to keep it moving forward.
The following principles are key to understanding aerodynamics:
- Smooth surfaces reduce drag: Rounded edges and uninterrupted panels guide air efficiently around the vehicle, minimizing drag.
- Gaps and cavities create turbulence: Open spaces between the cab and trailer, or under the trailer, create pockets of low pressure that suck energy from your forward motion.
- Tail-end design affects drag: Airflow that separates too sharply at the back of your trailer causes a vacuum effect that pulls your truck backward.
By minimizing drag through better design and equipment, you increase fuel economy and overall efficiency. That’s why truck manufacturers have invested heavily in factory-engineered aerodynamic features like sloped hoods and roof and side fairings.
How to Improve Semi Truck Aerodynamics
Opportunities exist to improve the aerodynamics of every semi truck, whether it’s a brand-new sleeper or a high-mileage day cab. Begin with the upgrades that give the best return on investment.
Focus on Tractor Aerodynamics
Truck manufacturers are increasingly placing focus on aerodynamics during the design process. Sloped hoods, cab extenders and high roofs are now standard features on many models designed for long-distance applications, helping to reduce drag and lower fuel consumption.
For non-aero models, there are many add-on devices and attachments that can improve the aerodynamics of your truck and streamline airflow around the cab. Investing in these devices can improve fuel economy by more than 3%, according to the EPA, making it easy to recoup their cost. Attachments that can improve aerodynamics on a standard semi tractor include:
- Roof Fairings/Rear Roof Extenders: Attach these to the top of the cab to create a smooth transition from the top of the windshield to the top of the trailer, preventing air from hitting the front of the trailer. Roof fairings are commonly used when there is a significant difference in the height of the cab and the trailer.
- Cab Extenders/Side Fairings: Attach these to the side of the cab, pointing backward toward the trailer. Cab extenders reduce the gap between the cab and trailer and are designed to prevent the development of crosswinds that cause drag.
- Chassis Fairings/Chassis Skirts: Attach these to the side of a tractor, typically spanning from the cab steps to the end of the cab. Chassis fairings cover the fuel tank, battery box and fenders, allowing air to flow smoothly over the lower portion of the cab.
- Drive Wheel Fairings: Mount these between and behind the drive wheels of a semi tractor to streamline airflow around the tires. Drive wheel fairings are often used in combination with wheel covers to provide fuel savings of up to 2%.
- Aerodynamic Bumpers: Reduce drag by swapping a flatter bumper with a curved one designed to match the shape of the underside of the hood and fender area.
Install Semi Trailer Aerodynamic Devices
Trailer devices are some of the most cost-effective aerodynamic tools for reducing drag. These devices improve fuel efficiency by lowering air resistance around the trailer so that it takes less fuel to propel the vehicle as speed increases. Aerodynamic trailer devices are especially helpful for long-haul routes where sustained highway speeds make drag a constant issue. When installed correctly and maintained, they pay for themselves quickly in fuel savings.
Side Skirts
Side skirts attach along the length of your trailer’s underside and are the most popular devices for addressing drag. They extend the trailer side walls closer to the ground to block airflow from becoming turbulent beneath the trailer. Trailer skirts have been found to improve fuel efficiency by 1% to 5%, according to the North American Council for Freight Efficiency.
Trailer Tails
Trailer tails (also called boat tails or rear fairings) extend from the back of the trailer and smooth out the air as it passes over the top and along the sides of the vehicle. They reduce the air wake field behind the trailer, which in turn reduces drag. Popularity of trailer tails has waned in recent years due to their operational complexity, but they have been found to provide at least marginal savings in fuel costs.
Gap Reducers
Nose cones and gap fairings are two types of aerodynamic devices designed to limit the air gap between the cab and trailer. They redirect airflow around the front of the trailer and reduce the turbulence in that space, improving efficiency and stability. According to the EPA, reducing the trailer gap from 45 to 25 inches can improve fuel economy by as much as 2%.
The importance of these gap-reducing devices has decreased for newer trailers, thanks to the aerodynamic improvements truck manufacturers have made to reduce the gap and achieve the same results.
Use Low-Resistance Tires, Wheel Covers and Mudflaps
Your tires cut through the air with every rotation. While that may seem minor, those little disruptions add up. Low-rolling-resistance tires are designed with stiffer sidewalls and specialized rubber compounds to reduce flex and energy loss.
In addition to fuel-friendly tires, consider smooth wheel covers. These reduce turbulence around your wheels and provide a cleaner surface for air to pass over. For tractors and trailers alike, they’re a simple addition that keeps airflow tighter to your rig’s surface.
While traditional mudflaps are made of solid rubber to prevent road debris from damaging the undercarriage, vented mudflaps feature small horizontal slits that allow air to pass through them while still serving their core purpose. Aerodynamic mudflaps haven’t been proven to significantly reduce fuel economy, but fleet adoption has steadily increased in an effort to improve overall airflow.
Keep Your Vehicle Maintained and Clean
Aerodynamics isn’t just about add-ons. Preventive maintenance plays a role, too. Loose panels or broken fairings can flutter at high speeds, adding unexpected drag. Excess dirt or grime can increase surface roughness, thereby reducing airflow efficiency. And debris-caked undercarriages create airflow disruptions that affect your entire trailer profile.
Keep your body panels secured, your fairings tight and your truck clean. Not only does this upkeep help with airflow, it shows professionalism and pride in your rig — something every seasoned driver respects.
Find the Right Truck at Rush Truck Centers
Improving semi truck aerodynamics doesn’t require a complete cab redesign. With targeted changes, such as adding side skirts, optimizing your cab-to-trailer gap or upgrading to low-resistance tires, you can trim fuel use and stretch every gallon further.
Whether you’re spec’ing a brand-new build or updating your trusted hauler, Rush Truck Centers is ready to help you move forward with confidence. With more than 140 commercial truck dealerships in 23 states, we stock new and used Class 7 and 8 semi trucks, vocational trucks and commercial vehicles from industry-leading brands, including Peterbilt, International, Hino, Isuzu and Ford.
View our current truck inventory to find the right truck for your route and bottom line.
COME ALONG FOR THE RIDE. Sign up to receive email updates with our latest promotions, blog posts and news from Rush Truck Centers.
