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Check whether slowing down is worth it for this truck, this diesel price, and this distance.
"My owner-operator reduced our truck speed from 105 to 100 km/h. Small change, big savings over a year."
Long-haul driver, Ontario
Average long-haul: 3,500-5,000 km/week
Loaded semi: 5.0-6.5 MPG · Empty: 7.0-8.0 MPG
Aerodynamic drag increases with the square of speed. Going from 100 to 110 km/h doesn’t use 10% more fuel. It uses about 13-15% more. Wind resistance at highway speed is the single biggest fuel consumer on a semi.
The sweet spot for most semis is 90-100 km/h (55-62 mph). Above that, every km/h costs you roughly 1.3% more fuel. Below 90, you barely save anything because engine efficiency drops.
Rule of thumb:
Dropping 5 km/h from highway speed saves about $2,000-4,000/year for a typical long-haul truck running 200,000+ km annually.
Other fuel-saving tips:
This calculator estimates fuel savings based on how speed affects drag. Results are estimates. Actual savings depend on load, terrain, wind, tire pressure, and driving style. Uses a 1.3% fuel penalty per km/h above 90 km/h, consistent with NRCan and DOE fleet studies.