New emissions standards for diesel engines have ushered in a whole new way of calculating fuel efficiency. Now tractors are judged by not only the “fuel” they consume, but also the “fluid” required to get emissions down to near-zero levels as required by the EPA’s Tier 4 emissions standards. It’s no small task, as tractor manufacturers have had to devote a large portion of their R&D dollars over the last decade to design engines that don’t smoke.

Tractor manufacturers have adopted one of two foundational technologies to date to meet the mandated cuts in particulate matter and oxides of nitrogen by the interim deadline of January 2011. One, called Selective Catalytic Reduction, or SCR, requires the use of an engine after-treatment called diesel exhaust fluid, or DEF, which is sprayed into the exhaust at a rate of 3% to 6% of fuel used, depending on load and operating conditions. Challenger, Case IH, Fendt, Massey Ferguson and New Holland use this strategy.

The other strategy, called Exhaust Gas Recirculation, or EGR, used by John Deere and Versatile, recirculates the exhaust gas before it leaves the engine to reduce nitrous oxides in the emissions. A diesel particulate filter is used to trap the soot. This regeneration cycle requires extra fuel, which the lab estimates is less than 1% of the total fuel consumed based on the fuel used during forced regenerations at three different load levels, as measured during the time of testing.

The big question now is, “How do these new tractors perform fuel-, or more accurately, fluid-wise?” Farm Industry News addressed that question using data from reports published by the Nebraska Tractor Test Lab, or NTTL, the officially designated tractor testing station for the U.S.

The lab had to revise its evaluation procedures in the past few years to account for the added fuel and DEF used in the tractors.

This report takes those fluids into account, and gives you the fluid efficiency ratings of the high-horsepower, or HHP, tractors (150 hp and up) that have been officially tested in the last five years, from 2009 to 2013.

Please note that only those models that have been tested are included in this report. So, if you don’t see a particular model in the lineup, it means it hasn’t been tested yet.

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Also, please note that both Tier 3 and Tier 4 interim tractors are included. Testing of Tier 4b engines will begin this spring, according to the NTTL.

As for Tier 4 interim tractors being better or worse on fuel, NTTL Director Roger Hoy says, “I really cannot make a general statement, except to say that DEF and fuel consumed during regenerations need to be considered along with fuel economy.”

We’ve divided the tractors into two categories based on chassis: row-crop tractors and HHP four-wheel drives. Ratings for the 4-wd tractors are published here:

Fluid-efficiency ratings for both groups ranged from 11 to 15 hp-hr./gal. As with fuel efficiency in cars, the higher the number, the better a tractor is on fuel or “fluid” economy. You must determine whether the fuel savings will ultimately justify a trade-in.

— Scott Grau, research manager at Penton Media, contributed to this report.

How fluid efficiency was calculated

Farm Industry News used data from reports published by the Nebraska Tractor Test Lab, or NTTL, in the last five years, from 2009 to 2013, to arrive at a measure that best reflects a tractor’s fluid efficiency. Fluid efficiency is the new term used by the lab that takes into account the diesel exhaust fluid and additional fuel consumed by tractors equipped with emissions-compliant engines. The Tier 4 interim standard went into effect in January 2011, and final standards came due this year. Only Tier 3 and Tier 4 interim engines are included in this report. Testing of Tier 4 final engines will begin this spring, according to the NTTL.

In 2011, the NTTL revised its reporting procedures to reflect the fluid efficiency accounting for the extra diesel fuel and diesel exhaust fluid used to meet EPA emissions standards. Fluid efficiency includes diesel fuel and, in the case of Tier 4a engines, diesel exhaust fluid, or DEF. Like fuel efficiency, fluid efficiency is measured in horsepower-hours per gallon (hp-hr./gal.). Measured directly, it means that burning 1 gal. of fuel or fluid in the tractor at full load and at rated engine speed produces a certain amount of horsepower for an hour. The higher the number, the greater the fuel or “fluid” efficiency; that is, more work is being done with a given amount of fuel or fluid.

The lab measures horsepower and fuel use at the PTO and drawbar, and at varying rates of power and pull to replicate the full range of field conditions. Fluid consumption at each operating point is obtained by dividing the power output (horsepower) by the fuel and fluid consumption (gallons per hour).

The NTTL provided us with the parameters on which operating points would best reflect a typical-use cycle for tractors in the size category of 150-plus hp. As such, fluid efficiency ratings for this report are based on “drawbar performance” at 75% of pull at maximum power to reflect performance during typical heavy fieldwork.

PTO numbers also are included for power comparisons and, in some cases where the tractor is being used primarily for PTO work, may be a better reflection of the amount of fluid burned during work.

DEF use was measured at the PTO at 85% and 63.75% resistance, and interpolated to come up with DEF use at the drawbar at 75% of pull at maximum power, fifth gear, which the NTTL would represent as typical field conditions. Where EGR is used, tractors are docked 1% for the fuel they use during regeneration.

HP was measured at the PTO at rated engine speed, which the lab says is a good indicator because it is one that is calculated for all tractors and is always run at the maximum level. Ratings will vary according to the intended use of the tractor. So the NTTL advises farmers to consider all operating points in the test report when making comparisons.

The ratings, published here or online, include all high-horsepower, row-crop tractors (over 150 hp) tested by the NTTL in the last five years. If a tractor model is not included in the chart, it means it hasn’t been tested yet.

The NTTL will not endorse or recommend any tractor.