Behind the Pump: Does Speeding Really Impact Your Bottom Line?

• kmiller4350
• Apr 24
• 2 min read

As fuel prices surge and we transition into our next busy season, finding ways to stretch every dollar and every gallon has never been more important. This brings us back to a question recently raised by a few of our own employees: Does strictly following the speed limit actually result in noticeable fuel savings?

While it is easy to follow the “pace of traffic,” the physics of fuel consumption tell a much more expensive story. Here is a look at the data behind aerodynamics, efficiency, and your wallet.

The Science of Aerodynamics

Fuel efficiency drops sharply as speed increases because wind resistance—or aerodynamic drag—rises exponentially. While your engine operates quite efficiently at approximately 55 mph, the effort required to push through the air increases significantly as you accelerate:

• At 70 mph: Aerodynamic drag is roughly 25% higher than at lower cruising speeds.
• At 80 mph: Drag is approximately 50% higher than it is at 60 mph.

Even a slight increase in speed forces the engine to burn significantly more fuel just to overcome this air resistance.

Benchmarking Your MPG

Most vehicles reach their peak fuel economy between 45–60 mph. Once you exceed 60 mph, the efficiency loss is consistent and measurable:

Speed	Estimated MPG Reduction
65 mph	~7% lower
70 mph	~10–15% lower
75 mph	~20% lower
80 mph	~25–30% lower

For example, if a truck typically averages 20 MPG at 65 mph, that same vehicle may drop to 17 MPG at 75 mph, and as low as 15 MPG at 80 mph. Over thousands of miles, these losses represent a significant operational cost.

The Economics of Slowing Down

To put this into perspective, consider the monthly cost for a driver covering 1,000 highway miles (using a conservative $3.00/gal estimate; costs are even higher at today’s rates):

Speed	MPG	Fuel Used	Monthly Cost
65 mph	20 mpg	50 gal	$150
75 mph	16 mpg	62.5 gal	$187

By simply adjusting your speed to the limit, you could save approximately $37 per month, or roughly $444 per year.

A simple rule of thumb to remember: Every 5 mph you drive over 60 mph is essentially like paying an extra $0.15 to $0.20 more per gallon of fuel.

Strategies for Better Efficiency

Beyond simply watching the speedometer, how you manage your throttle plays a major role in conservation.

• Maintain Steady Loads: Driving at or near the speed limit typically leads to less rapid acceleration and braking. Smoother engine load patterns alone can improve overall efficiency by 5–15%.
• Use Cruise Control Wisely: Use cruise control on flat terrain to maintain a constant speed. However, it is often more efficient to turn it off in hilly areas to prevent the engine from overshooting fuel consumption while trying to maintain a rigid speed on inclines.

Bottom Line

Does driving the speed limit save gas? Yes. Depending on your vehicle and cruising speed, you can save 10–30% on fuel costs by staying within the limit.

At Centra Sota, we are always looking for ways to help our community drive smarter and keep costs down. If you have other questions about equipment efficiency or energy use, reach out—we would love to do a deeper dive for you.