Running boards can cause a small decrease in fuel economy, typically in the range of 0–3% on highway driving, depending on design, weight, and how they’re mounted. Lighter, aerodynamic boards or OEM options tend to minimize the impact.
Running boards—also called side steps—add mass to the vehicle and alter airflow along the rocker area. This article looks at how those factors translate into miles-per-gallon changes and what buyers can consider when choosing and using running boards.
How running boards influence aerodynamics and weight
In this section we outline the physical factors that can influence fuel economy when running boards are present.
Before examining specific factors, consider the following list of what tends to affect the MPG impact of running boards:
- Weight of the board and mounting hardware, which increases the load the engine must move, especially during acceleration.
- Aerodynamic disruption from the board’s cross-section and mounting position, which can increase drag as air flows along the vehicle sides.
- Vehicle speed and driving style, with highway speeds magnifying aerodynamic effects and city driving amplifying weight penalties.
- Board design, including whether it is a low-profile, closed-form option or a bulky aftermarket style, and whether it is OEM-integrated or aftermarket.
- Vehicle type and mass; heavier trucks and SUVs may show smaller percentage changes even if the absolute drag is higher.
In practice, the MPG difference is usually small. The most noticeable changes occur at highway speeds where aerodynamic drag dominates fuel consumption, while city-miles-per-gallon are more sensitive to weight and drivetrain efficiency.
Design choices that minimize fuel economy impact
To reduce any potential MPG penalty, consider these design and installation factors when selecting running boards.
- Choose low-profile, narrow, and aerodynamically shaped boards that minimize cross-sectional area and turbulence.
- Prefer OEM-installed options or aftermarket boards that are specifically marketed as aerodynamically tuned.
- Ensure precise installation to reduce gaps, misalignment, or protrusions that can disrupt airflow.
- Consider retractable or flush-mounted designs if available, as these typically offer the smallest drag penalty when not in use.
- Keep the weight as low as possible by selecting lightweight materials and avoiding unnecessarily heavy hardware.
Ultimately, for drivers where MPG is a priority, it’s worth weighing the convenience of easier access against a small, sometimes negligible, fuel-economy penalty. For many users, the benefit of easier ingress and egress outweighs the potential cost in fuel efficiency.
Summary
Do running boards decrease MPG? Yes, but the effect is typically modest. Expect a small decrease in highway fuel economy—often less than a few percent—driven by added weight and aerodynamic drag. The exact impact depends on board design, mounting, and vehicle type. By opting for lightweight, aerodynamically optimized designs and ensuring proper installation, drivers can minimize the MPG penalty while enjoying the added convenience of easier access.