How Driving Speed Affects RV Fuel Consumption

Meta Description: The speed-fuel curve for motorhomes explained so you can find your optimal cruising speed. How driving speed affects RV fuel consumption.

When you are driving a machine that essentially has the aerodynamic profile of a concrete block, the most crucial variable in your fuel economy equation is your right foot. Pushing the speedometer past 60 MPH often yields heavily diminishing returns.

The Physics of Wind Resistance

Aerodynamic drag does not increase linearly with speed; it increases exponentially. This means the engine power (and fuel) required to push an RV through the air from 60 MPH to 70 MPH is vastly more than what is required to go from 50 MPH to 60 MPH.

At approximately 55 MPH, the dominant force opposing your RV shifts from tire rolling resistance to wind friction. Above 55 MPH, the vast majority of your engine's output and fuel is being spent simply punching a hole through the air.

The Speed-to-MPG Ratio

While every RV class and engine configuration varies slightly, the general industry consensus follows a reliable formula:

• For every 1 MPH you drive over 55 MPH, your fuel economy decreases by roughly 1% to 1.5%.
• Therefore, driving at 65 MPH instead of 55 MPH could decrease your overall MPG by roughly 10% to 15%.
• If you average 8 MPG at 55 MPH, pushing the speed to 65 MPH might drop your efficiency down to 6.8 MPG, significantly shrinking your safe travel range.

Gearing and the "Sweet Spot"

Every engine and transmission combination has an optimal RPM range called the "sweet spot"—the speed where the engine produces enough torque to maintain highway speeds while hovering in the lowest possible RPM in overdrive gear.

For most gas Class A and Class C motorhomes, this sweet spot is noticeably around 55 MPH to 60 MPH. For larger diesel pushers, which produce massive amounts of low-end torque, the sweet spot might be marginally higher, around 62 MPH to 64 MPH.

Safety Factor

Beyond strictly financial savings, stopping distances in heavy motorhomes improve drastically when traveling at 60 MPH opposed to 75 MPH. RV tires (specifically trailer tires) are also frequently rated for maximum speeds of only 65 MPH, making faster travel highly dangerous regarding blowout risk.