‘Gearing up, throttling down’ saves fuel, keeps input costs lower

BLACKSBURG, Va. – Fuel prices this year have kept everyone guessing. They are making it particularly hard for farmers to keep their fuel costs in line with input budgets.

Bobby Grisso, who just joined Virginia Tech as an agricultural engineer, offers farmers an operating technique that can save them 15 percent to 25 percent on tractor fuel.

“Gearing up and throttling down can help lower their fuel use this season,” said Grisso. “The practice uses 15 percent to 25 percent less energy than operating tractors at full power.”

The practice is effective for light operations such as planting, cultivating, spraying, and some light tillage that do not require full power. For these tasks, farmers can save fuel by shifting to a faster gear and slowing the engine speed.

“By doing this, you’re allowing the engine to operate at its most fuel-efficient level,” Grisso explains.

Nebraska numbers. Tests conducted by the Nebraska Tractor Test Lab showed that a 110-power-takeoff (PTO) horsepower tractor pulling 50 percent of its maximum drawbar load at full throttle used 4.5 gallons of fuel per hour.

PTO horsepower is the amount of power a tractor’s PTO delivers.

That same tractor pulling 50 percent at a reduced throttle setting used only 3.7 gallons of fuel per hour, saving three-fourths of a gallon per hour.

The savings add up quickly during the long days of summer, Grisso said. Assume a home-delivery fuel price of $1.09. Producers would save $7.36 in a nine-hour workday.

When not to ‘gear up.’ Grisso said the practice shouldn’t be used when the PTO is operating, such as during hay harvesting. The PTO will run correspondingly slower when the engine speed decreases and may not provide enough power to properly run PTO-driven equipment.

Gearing up and throttling down also can damage the engine by creating too much torque when using PTO-powered equipment.

Operators also should avoid overloading or “lugging” the engine, according to Grisso. To check for overload, he suggests running the tractor using the desired speed and throttle setting and opening the engine to full throttle. If the engine rapidly picks up speed, the setting is appropriate. A slow response or black smoke indicates a problem.

To resolve the problem, shift down a gear or increase the engine’s speed, he said.