Although high fuel prices have driven up production costs, there is some good news in the field: Farm tractors are steadily becoming more fuel-efficient. According to a study by the University of Nebraska Tractor Test Laboratory (NTTL), models designed in 2000 averaged 16.54 hp hrs./gal., compared to 1980 models, which averaged 14.48 hp hrs./gal. Meanwhile, passenger vehicles are sucking up more gas than they did in the past; their average number of miles per gallon has dropped to a 20-year low. You could say that farm tractors, in comparison, look downright frugal.
Competing for the lowest rate
Although torque, drawbar and PTO horsepower will always be the gold standards for gauging tractor performance, many tractor companies are now also likely to boast about their fuel economy ratings. Earlier this year, Case IH claimed its STX Steiger posted the lowest fuel consumption at maximum power among tractors with 400 or more horsepower evaluated at the NTTL.
“The Nebraska tests have long been regarded as a ‘consumer report’ for new agricultural tractors,” says Randy Wood, Case IH product marketing manager. “These tractors were designed with the input of 2,200 farmers. The result is unsurpassed productivity, fuel economy and ease of operation.”
For now, Case is enjoying its moment in the sun. But the performance and fuel economy shootout among tractor companies is likely to be a see-saw battle as new models from different companies put their efficiency and power to the test each year.
Multiple university studies show that, when you upgrade from a 10-year-old tractor to a new one, on average you will save 10 to 15% or more fuel based on improved engine design and optimal operational matching. Although you probably can't justify buying a new tractor based on fuel savings alone, potential fuel savings on an hourly basis is one factor to consider. As you sort through all the tractor company claims and pore over spec sheets, the figure you want to look for, according to NTTL test engineer Bret Sampson, is “horsepower hours per gallon.”
Figuring fuel economy
“Horsepower hours per gallon is a tractor's equivalent of an automobile's miles-per-gallon rating,” Sampson says. “It refers to the amount of fuel needed to produce power. When you read the specs, a higher horsepower-hours-per-gallon number means better fuel efficiency.” Sampson warns that you have to be careful about which number you look at. “The ‘engineering community’ uses a different measure called the spec fuel value, which factors out the difference in fuel weight,” he explains. “On spec fuel value, the lower the number, the better.”
For demonstration purposes, Sampson compares reports from four high-horsepower diesel tractors: Case IH STX440, Case IH STX Quadtrac, John Deere 9400 Powersync and Caterpillar Challenger 95E (see table).
When you're considering the actual work each machine can do for the fuel it burns, one interesting comparison is on drawbar performance. “The 440 Quadtrac STX is 26 hp less than the 440 STX wheel model,” Sampson says, “even though both were at 400 on the PTO. Ballast increases the maximum pull in almost direct relation to the amount added, but only slightly increases the maximum horsepower in most cases. The 440 STX wheel actually lost 2 hp with the addition of ballast.”
Sampson says the weight of the tractor also figures into the equation. “The 440 STX Quadtrac pulled 38,412 lbs. [electronically limited] with a tractor weight of 51,530, while the 440 STX wheel model pulled 40,035 lbs. with a tractor weight of 39,500.” Generally, lighter tractors get better fuel economy.
Case is quick to point out that its STX machine outpulled the Cat 95E, which had an unballasted weight of 36,050 lbs.
To get a good comparison of power train efficiencies, it also helps to compare the power developed, and the fuel economy, on the PTO versus the drawbar.
“Our figures show that John Deere and Case seem to be able to get 92% of PTO power on the ground with their wheel models, with the Quadtrac at 86%,” Sampson says. “It takes power [and fuel] to turn all those rollers and bend those tracks!”
The NTTL assesses power takeoff performance, drawbar performance and 3-pt. hitch performance under varying loads and engine speeds. The lab sells its reports at a price of $15 for five tractors, allowing prospective tractor buyers an opportunity to compare performance of competitive products on an even playing field. To order reports, contact Nebraska Tractor Test Laboratory, Dept. FIN, Box 830832, Lincoln, NE 68583, 402/472-2442, e-mail tractortest email@example.com.
Fuel efficiency at rated engine speed*
|Model||PTO rated engine speed (hp hrs./gal.)||Drawbar, unballasted, max power (hp hrs./gal.)|
|Case IH STX440||18.11||17.03|
|Case IH STX440 Quadtrac||18.12||15.61|
|Caterpillar Challenger 95E||19.01||17.03|
|John Deere 9400 Powersync||18.15||17.01|
|*Data from the Nebraska Tractor Test Laboratory|