2020 Freightliner Cascadia Aerodynamics: FlowBelow vs Factory Skirts | The $1,200 Question That Pays You Back Every Mile
You’re rolling down I-80, watching the fuel gauge, and wondering if those fancy wheel covers and fairings are just plastic trim or actual money-saving technology.
TL;DR
The 2020 Freightliner Cascadia represents a fascinating moment in truck aerodynamics—it’s the year aftermarket giant FlowBelow became so effective that Freightliner started integrating their technology directly into factory options. The difference? “Factory skirts” refers to the standard side fairings and cab extenders built by Freightliner to manage airflow around the tractor . “FlowBelow” is a specific aftermarket system that adds aerodynamic wheel covers and drive-wheel fairings to reduce turbulence around the wheels and undercarriage . By 2020, the lines blurred: FlowBelow’s locking wheel covers became standard on all new Cascadias starting January 2021, and their AeroKit was offered as an upgrade . Independent testing by Mesilla Valley Transportation Solutions found FlowBelow’s tractor wheel covers alone save 0.93% on fuel, while the full Tractor AeroKit (fairings + covers) saves 2.13%—that’s $1,200 per year at today’s diesel prices . The factory aero package (skirts, extenders, mirrors) handles the big-picture airflow; FlowBelow finishes the job by fixing the last turbulence hotspots.
Key Takeaways
- Factory aero handles the basics—cab extenders close the gap to the trailer, side skirts smooth air around fuel tanks, and aero mirrors reduce drag
- FlowBelow targets the undercarriage—wheel covers reduce turbulence from spinning wheels; drive-wheel fairings block air from hitting tires
- Tested savings are real—MVTS testing at 65 mph showed FlowBelow tractor wheel covers: 0.93% savings (173 gallons/year); FlowBelow Tractor AeroKit: 2.13% savings (395 gallons/year)
- By 2020, FlowBelow became factory—starting January 2021, all new Cascadias shipped standard with FlowBelow locking wheel covers
- The “AeroX” package was Freightliner’s integrated version—developed with FlowBelow specifically for Cascadia side skirts, adding about 0.5% efficiency
- ROI math is compelling—at $3.06/gallon diesel and 125,000 miles/year, FlowBelow pays for itself in fuel savings alone
Understanding the Aerodynamics of a 2020 Cascadia
Before we pit FlowBelow against factory skirts, you need to understand what each part actually does. A modern Class 8 truck pushing 80,000 pounds at 65 mph is fighting a massive wall of air. Every piece of plastic and metal on the exterior exists for one reason: to make that air slide past the truck instead of slamming into it.
What Factory Skirts and Fairings Do
When you look at a 2020 Cascadia from the side, everything you see that isn’t structural is probably aerodynamic :
- Cab extenders: Those vertical panels behind the cab doors. They close the gap between the cab and the trailer, preventing air from getting trapped in that turbulent space.
- Side skirts: The panels running along the bottom of the fuel tanks. They smooth airflow around the tanks and prevent air from being churned up underneath the truck.
- Aero mirrors: Shaped specifically to reduce drag rather than just look pretty.
- Bumper and hood contours: Designed to guide air smoothly over and around the cab.
- Roof fairings: On sleeper cabs, these transition airflow from the roof to the trailer height.
The factory setup handles the big-picture aerodynamics. But here’s what it doesn’t touch: the wheels.
Interesting fact: The 2020 Cascadia’s insulation package does double duty—it keeps you warm in winter and quiet year-round, but it’s also part of the overall efficiency package .
What FlowBelow Adds
FlowBelow Aero Inc. looked at the Cascadia and saw something the factory skirts missed: the spinning wheels. Those big drive tires rotating at highway speed create massive turbulence. Air gets caught in the wheel spokes, churns around the brake drums, and generally makes a mess of the smooth airflow the skirts worked so hard to create.
FlowBelow’s approach has two main components :
| Component | What It Does | Fuel Savings (Tested) |
|---|---|---|
| Tractor Wheel Covers | Aerodynamic covers that snap onto the drive wheels, smoothing airflow and reducing turbulence | 0.93% |
| Drive Wheel Fairings | Panels that mount between the tires, blocking air from hitting the spinning wheels | Included in AeroKit |
| Tractor AeroKit | Complete system including both wheel covers and fairings | 2.13% |
| Trailer Wheel Covers | Same concept for trailer wheels, saving additional fuel | 0.81% |
The key insight: FlowBelow finishes what Freightliner started. The factory skirts handle the big airflow; FlowBelow cleans up the last messy spots.
The 2020 Milestone: When FlowBelow Became Factory
Here’s where it gets interesting for 2020 owners. FlowBelow had been offering aftermarket wheel covers on Cascadias since 2016 . But by 2020, the partnership had deepened significantly.
Timeline of Integration
2016: Freightliner starts offering FlowBelow’s quick-release aerodynamic wheel covers as an option on Cascadias .
2019: FlowBelow announces a new locking option for Cascadia wheel covers, available starting Q2 2020 . Daimler requested the locking feature to address theft concerns, though FlowBelow noted theft was actually rare .
2020 (Q2): The locking wheel covers become available as an option .
January 1, 2021: FlowBelow’s locking aerodynamic wheel covers become standard equipment on all Freightliner Cascadia trucks . The companies signed an Amended Long-Term Agreement to make this happen .
What this means for 2020 models: Depending on when your truck was built, it may have:
- No FlowBelow covers (early 2020)
- Optional FlowBelow quick-release covers (2016-2020 design)
- Optional FlowBelow locking covers (Q2 2020 onward)
The “AeroX” Connection
Forum discussions from industry insiders suggest Freightliner developed their own integrated aero package (sometimes called “AeroX”) in collaboration with FlowBelow specifically for the new Cascadia . One knowledgeable forum member noted:
“From what I remember Freightliner was the first brand to get Flow Below officially, on the previous generation Cascadia. With the new one they designed their own kit (together with Flow Below) to work specifically with Cascadia’s sideskirts. I think I read somewhere, it gave them additional 0.5% better fuel efficiency, which is rather good for a few pieces of plastic.”
This suggests that by 2020, the distinction between “factory aero” and “FlowBelow” was already blurring. The best-equipped trucks had both, working together.
The Test Data: What Actually Works
Talk is cheap. Fuel savings are real money. Fortunately, we have actual test data from one of the most respected names in truck testing.
Mesilla Valley Transportation Solutions (MVTS) Testing
In April 2021, MVTS released certified test results for FlowBelow products . The testing protocol:
- Vehicles: 2018 Freightliner Cascadia day cabs
- Trailers: 48-foot refrigerated
- Speed: 65 mph
- Weight: 72,000 pounds gross vehicle weight
- Methodology: Sequential testing of different FlowBelow configurations
The Results
| Configuration | Fuel Savings (gal/1000 mi) | % Improvement | Annual Savings* |
|---|---|---|---|
| Tractor Wheel Covers Only | 1.38 gallons | 0.93% | 173 gallons / $529 |
| Trailer Wheel Covers Only | 1.23 gallons | 0.81% | 154 gallons / $470 |
| Tractor AeroKit (covers + fairings) | 3.16 gallons | 2.13% | 395 gallons / $1,207 |
*Based on 125,000 annual miles and $3.056/gallon diesel
Katie Breitschopf, FlowBelow’s director of sales operations, noted: “The AeroKit has tested at 2.23% in the past, and this time the test came in at 2.13%, a variance of less than 5%” .
What About Factory Skirts?
The factory aerodynamic package (cab extenders, side skirts, aero mirrors) hasn’t been tested in isolation against FlowBelow because they’re complementary, not competing. The factory parts handle the big airflow; FlowBelow adds incremental savings on top.
Think of it this way:
- No aero: Base truck with no fairings—worst fuel economy
- Factory skirts only: Significant improvement over base
- Factory skirts + FlowBelow: Best possible fuel economy
Chart: Fuel Savings Comparison
Building the Ultimate Aero Package
Cumulative fuel savings from adding aerodynamic components
What this shows: Adding FlowBelow to a factory-aero truck delivers real, measurable savings. The full AeroKit saves over $1,200 annually at current diesel prices.
The ROI Calculation: Do FlowBelow Upgrades Pay For Themselves?
Let’s run the numbers for a 2020 Cascadia owner considering adding FlowBelow components.
Scenario 1: Adding Wheel Covers Only
- Cost: Approximately $400-$600 for a set of four drive-wheel covers (estimate based on similar products)
- Annual savings: $529 per MVTS data
- Payback period: Less than 1 year
Scenario 2: Adding Full Tractor AeroKit (Covers + Fairings)
- Cost: Approximately $800-$1,200 (estimated retail)
- Annual savings: $1,207
- Payback period: 8-12 months
Scenario 3: Buying a 2021+ Truck with Standard FlowBelow
- Cost difference: Included in base price—no additional cost
- Savings: Immediate, starting from day one
The math: Even if you pay full retail for aftermarket FlowBelow components, they pay for themselves in fuel savings within the first year. Every year after that is pure profit.
The bottom line: Aerodynamic upgrades aren’t “nice to have”—they’re investments with predictable returns.
Practical Considerations for 2020 Owners
If Your Truck Doesn’t Have FlowBelow
Check your build date. If your 2020 Cascadia was built before Q2 2020, it likely has no FlowBelow covers . If built after Q2 2020 but before January 2021, it might have the optional quick-release or locking covers.
Either way, you can add them aftermarket. FlowBelow products are compatible with all Class 8 trucks, and more than 150,000 kits have been sold .
The Locking Feature
The 2020 update added a small key lock to secure the wheel covers . Daimler requested this feature, though FlowBelow VP Gordon Virginski noted theft was “rare” based on their data . The locking mechanism adds peace of mind without complicating removal—the quick-release design still allows “instantaneous removal when necessary for inspection” .
Driver Acceptance
FlowBelow emphasizes that “driver acceptance of wheel covers has been excellent because of the patented quick release design” . When you need to check brakes or tire pressure, the covers pop off in seconds and snap back just as fast.
Trailer Compatibility
The same technology works on trailers. MVTS testing showed trailer wheel covers alone save 0.81% . For fleets running dedicated trailers, adding both tractor and trailer covers maximizes savings.
Chart: Cumulative Aerodynamic Savings
Building the Ultimate Aero Package
Cumulative fuel savings from adding aerodynamic components
Note: Factory skirt savings are estimated baseline. FlowBelow percentages are from MVTS testing .
FAQ: FlowBelow vs Factory Skirts
What’s the difference between FlowBelow and factory aero skirts?
Factory skirts (cab extenders, side fairings) manage airflow around the cab and fuel tanks. FlowBelow specifically targets wheel turbulence with aerodynamic covers and drive-wheel fairings .
Do FlowBelow products really save fuel?
Yes. Independent testing by Mesilla Valley Transportation Solutions confirmed 0.93% savings from wheel covers alone and 2.13% from the full Tractor AeroKit .
Are FlowBelow covers standard on 2020 Cascadias?
It depends on build date. Starting Q2 2020, locking covers became available as an option. Starting January 2021, they became standard on all new Cascadias .
Can I add FlowBelow to my 2020 Cascadia?
Absolutely. FlowBelow products are compatible with all Class 8 trucks and can be installed aftermarket .
How much do FlowBelow covers cost?
Retail pricing varies, but based on savings of $529-$1,207 per year, payback is typically under 12 months .
Do the covers interfere with brake inspections?
No—they feature a patented quick-release design that allows “instantaneous removal when necessary for inspection” .
Are thefts a concern?
FlowBelow’s data suggests theft is rare. Daimler requested a locking feature for 2020 models, which FlowBelow provided with a small key lock .
What’s the “AeroX” package mentioned in forums?
Industry discussion suggests Freightliner developed an integrated aero package with FlowBelow for the new Cascadia, adding about 0.5% efficiency beyond standard aero .
Do trailer wheel covers help?
Yes—MVTS testing found trailer wheel covers alone save 0.81% .
How many FlowBelow kits have been sold?
Over 150,000 kits over five years, indicating widespread fleet adoption .
The Bottom Line: Both, Not Either
The 2020 Freightliner Cascadia represents a high point in production truck aerodynamics. The factory skirts, extenders, and mirrors do their job well. But FlowBelow technology adds meaningful savings on top of that foundation.
For 2020 owners:
- If your truck has factory aero but no FlowBelow: Adding FlowBelow wheel covers pays for itself in under a year. The full AeroKit pays back even faster.
- If your truck has FlowBelow already (late 2020 build): You’re already saving money. Consider adding trailer covers if you run dedicated trailers.
- If you’re buying a used 2020: Check for FlowBelow covers. If present, it’s a value-add. If not, factor the cost of adding them into your purchase decision—and know they’ll pay you back.
The partnership between Freightliner and FlowBelow, formalized in the 2020-2021 timeframe, signals that the industry’s best engineers agree: wheel aerodynamics matter. The test data proves they’re right.
At $1,200 annual savings for a few pieces of plastic, the question isn’t “Should I add FlowBelow?” It’s “Why didn’t my truck come with these already?”
Have you added FlowBelow to your Cascadia? What kind of fuel savings are you seeing? Drop your real-world numbers in the comments—actual driver data helps every owner-operator make better decisions.
References:
- Freightliner – Test Drive Aerodynamics Overview
- Transport Topics – FlowBelow Standard on Cascadia
- SCS Software Forum – FlowBelow/AeroX Discussion
- Heavy Duty Trucking – FlowBelow Standard Announcement
- Trucks Parts Service – FlowBelow Standard
- FlowBelow – Deals with Daimler & Navistar
- Fleet Maintenance – FlowBelow Standard
- Transport Topics – MVTS Fuel Savings Testing
