Fuel Economy by Speed Calculator

Driving faster burns more fuel — the Fuel Economy by Speed Calculator shows exactly how much more it costs you. Enter your car's highway MPG, daily highway miles, and gas price, then select a speed range to compare to see your daily fuel cost at optimal speed (55 MPH), daily cost at 80 MPH, yearly savings between those two speeds, and the efficiency loss percentage at higher speeds.

mpg

EPA highway fuel economy rating for your vehicle

miles

Highway miles you drive per day

per gallon

Results

Daily Cost at Optimal Speed (55 MPH)

--

Daily Cost at 80 MPH

--

Yearly Savings (55 vs 80 MPH)

--

Efficiency Loss at 80 MPH

--

Results Table

More Automotive Tools

Frequently Asked Questions

What is the most fuel-efficient driving speed?

For most vehicles, the optimal fuel economy occurs between 55-60 mph. This is when your engine operates most efficiently, balancing power output with minimal fuel consumption.

How much does speeding affect fuel economy?

According to Department of Energy studies, fuel economy decreases rapidly above 60 mph. At 70 mph, you lose about 17% efficiency, and at 80 mph, you lose about 28% compared to 55 mph.

How much money can I save by driving slower?

The savings depend on your driving habits and local gas prices. Typically, reducing highway speed from 80 to 60 mph can save hundreds of dollars per year for regular commuters.

Why does fuel economy decrease at higher speeds?

At higher speeds, your engine works harder to overcome increased air resistance (drag), which increases exponentially with speed. This requires more fuel to maintain the higher velocity.

Does this apply to all types of vehicles?

While the general principle applies to most vehicles, the exact optimal speed can vary. Larger vehicles and trucks may see peak efficiency at slightly lower speeds due to their aerodynamics and weight.

How accurate are these fuel economy calculations?

These calculations are estimates based on EPA data and Department of Energy research. Real-world results may vary due to driving conditions, vehicle maintenance, weather, and individual driving habits.

What other factors affect fuel economy besides speed?

Tire pressure, vehicle maintenance, air conditioning use, cargo weight, aggressive driving (rapid acceleration/braking), and weather conditions all significantly impact fuel economy.