Bug deflectors get mixed reviews. Detractors complain that they don’t work as advertised and only burden fuel usage. Others counter that bug deflectors are effective and have zero impact on your fuel economy.
With so much conflicting information, you want the straight facts on bug deflectors. So the ultimate question: do bug shields hurt gas mileage? Yes. But only slightly.
To better understand how bug deflectors affect your gas mileage, we can look at how they work. When driving, air moves across your hood and over your windshield (see the above picture for an example). Bug deflectors disrupt this airflow, skipping air over your windshield and onto your roof.
This wind deflection is similar to how a rear spoiler might work. A spoiler decreases drag and improves speed, making them popular in sports like NASCAR. These deflectors “spoil” the turbulence behind a fast vehicle, giving racers a slight advantage.
Bug deflectors are not as reliable as spoilers. Instead, bug deflectors increase drag, which makes your truck less fuel efficient. How much fuel efficiency are you losing?
If you’ve wondered why there are so many differing opinions on bug deflectors, these three variables might explain why.
Speed. Aerodynamic drag will not have a noticeable impact until you reach roughly 45 mph. If you rarely take your truck on the highway or rarely drive above 55 mph, it’s unlikely your fuel economy will change.
Your truck’s design. As technology advances, trucks become increasingly aerodynamic. If you have a newer, more streamlined truck, installing a bug deflector could cause a noticeable difference in gas mileage. Older trucks might not see any change.
The deflector’s design. Bug deflectors should go through wind tunnel testing to determine aerodynamics. Testing a product in a wind tunnel is expensive and can rack up thousands of dollars. Some bug deflector brands might skip wind tunnel testing to save money. They rely on computer modeling or guesswork instead.
If you’re interested in buying a bug deflector, purchase one that is high-quality and wind tunnel tested. Cheap, “bargain bin” deflectors will probably cause more drag.
We can back these claims up with hard data too. The National Research Council of Canada did their own research. In order to determine the impact add-ons like bug deflectors have on fuel economy, they performed wind tunnel testing on commercial trucks. They found that bug deflectors only decrease fuel economy by 1.5-3% (on average). Most drivers won’t notice a difference that small.
Can You Buy a Bug Shield That Doesn’t Hurt Gas Mileage?
Bug deflectors will always reduce fuel economy. It is inescapable. But you can take steps to reduce that impact on your gas mileage:
Buy a deflector that’s been wind tunnel tested. Many deflectors on the market don’t do wind tunnel testing, which means they’re more likely to hurt your gas mileage.
Save gas by making other modifications. If you’re worried about your fuel economy, there are other ways to save gas. Installing low rolling resistance tires can boost your fuel economy 2-3%, which potentially makes up for any negative impact a deflector has.
Believe it or not, you can also improve your truck’s airflow by installing running boards.
“GM says Tonneau covers for the bed help smooth airflow over the truck, and Bloch says soft covers are more beneficial than the hard ones because they “form to how the air wants to flow.” Round, tube-style running boards can also help air flow smoothly down the truck’s sides, but flush-mount running boards are even better.”
Lift kits and oversized wheels/tires can further damage your truck’s fuel economy. Driving without these add-ons helps you save gas.
Ultimately, bug deflectors have a minimal impact on your gas. If you invest in a high-quality deflector, you’ll get a product that works well and won’t cost you too much at the fuel station.