Do Mudflaps Tank Your Truck’s MPG? This Super Scientific Aero Breakdown Has Answers

With gas and diesel prices soaring, fuel consumption is back on people’s minds. One way to improve efficiency and keep that fuel consumption to a minimum is by reducing aerodynamic drag. Giving an existing vehicle sleek new bodywork is probably out of reach for most people, but small changes can help, as this analysis from Premier Aerodynamics shows.

The airflow analysis specialists at Premier Aerodynamics use OpenFOAM, an open-source computational fluid dynamics (CFD) program, to do things like demonstrate that the second-generation Dodge Dakota is actually more aerodynamic than it seems. This time, they stayed on the topic of pickup trucks by tackling the question: Will removing mud flaps increase mpg?

To find out, Premier Aerodynamics ran a simulation of a recent Toyota Hilux (specifically the eighth-generation version that’s just now being replaced) at 100 kph. That’s 62 mph—or highway speeds, in other words. The Hilux isn’t sold in the United States, but it’s a reasonable analog for midsize pickups that are, like the Toyota Tacoma.

The analysis found that mud flaps generated more aerodynamic drag, but the effect was fairly small compared to that of the Hilux’s tall ride height, which generated big wakes around the wheels. The mud flaps added to this—particularly disrupting airflow higher off the ground—but it was essentially making an existing problem worse. Nonetheless, mud flaps increased the coefficient of drag from 0.37 to 0.38, and removing them could save $70 a year in fuel costs assuming most driving is done at highway speeds, the host says in a video explaining the findings.

How Much Do Mudflaps Increase Your Fuel Consumption?

Other changes might yield bigger gains in mpg, though. The host advocates covering the bed—especially with one of those (admittedly goofy-looking) fastback bed covers—or lowering the ride height. The eighth-gen Hilux’s pronounced wheel arches and sharply angled A-pillars also came in for criticism. Both are styling features that don’t serve a functional purpose, but do contribute to aerodynamic drag. It would be interesting to see how the restyled ninth-generation Hilux compares.

Like that Dakota, though, the truck simulated here performed better than appearances might suggest. The front end does a good job of keeping airflow attached (only for it to bleed off behind the front wheels due to the ride height), the body line between the rear wheel well and tailgate slopes up to act like a diffuser, and the airflow over the bed is well-managed. Sometimes automakers know what they’re doing.