When people talk about tractor fuel, the question is usually “how many litres an hour does it burn?” In farm work, though, the question that really matters is a different one: how many litres does it take me to work one decare? A machine that burns little per hour but works slowly can cost more per decare than one that burns a little more per hour but gets the job done quickly.
In this guide we explain how to measure consumption per decare on a tracked tractor correctly first, and then how to bring it down. In the examples we use the QD35 tracked tractor: a 35 HP, single-cylinder, water-cooled diesel engine, a 16-litre fuel tank and fuel consumption of 1–2 litres per decare in the specification table. Which end of that range you work at is largely up to you.
Measure first: how do you calculate tractor fuel consumption per decare?
You can’t reduce what you don’t measure. The most reliable method is the full-tank method:
- Before starting work, fill the tank to the brim with the machine standing on level ground.
- Do the job and note down the area you have worked in decares.
- Bring the machine back to the same level spot and fill the tank to the brim again.
- Divide the litres you added by the decares worked. The result is the consumption per decare for that job.
Measure each type of job separately. Rotary tilling, ploughing, weed clearing and haulage use very different amounts of fuel; lumping them all into one average hides what needs improving. Your first few measurements give you a real baseline for your own field and your own work.
Example calculation: With the 1–2 litres per decare in the specification table, a 16-litre tank means roughly 8 to 16 decares of work. The real figure varies with the soil, the job and the settings; compare it with your own measurement. If the area you work per tank on the same job falls during the season, that is a sign that something has changed.
Two common mistakes spoil the measurement. The first is filling the tank on different slopes: a tank filled “to the brim” on a slope doesn’t take the same amount as one on level ground. The second is estimating the area worked by eye. Take the plot area from the title deed, or walk the boundaries with a phone app that measures area; if you only worked part of the plot, calculate that part separately.
Five factors that determine consumption
- Type of job and depth: The deeper and finer you work the soil, the harder the engine has to work. Tilling deeper and with more passes than needed is the most common reason consumption climbs to the top of the range.
- Soil condition: In wet, sticky soil the tracks slip; every metre of slip is fuel burnt for nothing. Very dry, hard soil also strains the attachment and the engine.
- Choice of gear and engine speed: Doing the same job in the wrong gear either labours the engine or runs it at needlessly high revs.
- Working pattern: Running empty, unnecessary turns, trips between the field and the village for fuel.
- Machine condition: A clogged air filter, a slipping belt, over-tight tracks, blunt blades.
The first two of these five factors are about tillage technique, and we cover them in detail in our guides to soil preparation with a rotavator and ploughing. Here we focus on the other three.
Gear and engine speed: run the engine at the right load
A diesel engine is efficient neither when it is labouring nor when it is revving high with no load. The aim is to do the work without straining the engine, but without revving it for nothing either.
- If the engine is labouring (the revs drop noticeably, dark smoke comes from the exhaust, the machine judders), drop down a gear. A labouring engine can’t burn its fuel completely; consumption goes up and the engine wears.
- If the load is light (running back empty, a light trailer, haulage on a level road), shifting up a gear and easing off the throttle usually saves fuel. If the engine is pulling comfortably, there is no benefit in keeping it at high revs.
- With rotating attachments (such as a rotary tiller), the engine may need to be kept at the operating speed recommended in the manual so that the attachment turns at the right speed. In that case, adjust the load by choosing a lower travel gear, not by lowering the engine speed.
The QD35’s 3 forward and 1 reverse gears, combined with the high/low range, give 8 different options; the engine’s rated speed is 2,200 rpm. For each job, find the best gear in your own soil by trying it once, and write it down. You won’t need to experiment again the next season.
Idling burns fuel too
Every minute the engine spends idling burns fuel and runs up the hour meter, but produces no work. Don’t leave the engine running for long while chatting, on the phone or waiting. The only exception is letting an engine that has been working under heavy load idle briefly to cool down before you switch it off.
Operator habits: same machine, different consumption
The same tractor in the same field can use noticeably different amounts of fuel with two different operators. The habits that make the difference are often small:
- Smooth throttle: Jabbing at the throttle and letting it off makes the engine burn extra fuel every time. Open the throttle gradually and hold it steady.
- No riding the clutch: Moving along with a slipping clutch heats and wears the clutch and turns part of the engine’s power into heat.
- Reading ahead: Seeing the end of the row, obstacles and turns in advance and adjusting your speed in good time cuts down on hard braking and re-accelerating.
- Short warm-up: Rather than warming the engine up at idle for a long time, it is usually more efficient to work at light load for the first few minutes after a short warm-up; in cold weather, follow the recommendation in the manual.
- Not carrying unnecessary loads: Don’t leave materials and equipment you won’t need for the day’s work on the machine or in the trailer.
If more than one person uses the machine, talk these habits through together and note in the fuel log who was operating. Seeing the difference between operators brings the fastest improvement.
Field layout: cut down the metres travelled for nothing
A large part of the fuel difference between two operators working the same field comes from the metres the machine travels without doing any work:
- Work along the long side. Long strips let you work the same area with fewer turns. Every turn is time and fuel spent without doing any work. Example (hypothetical figures): If you work the same area in 50-metre strips instead of 100-metre strips, the number of turns doubles.
- Plan your turns. At the end of the row, a wide, flowing turn instead of a sharp turn on the spot spares both the tracks and your time. Leave the headland until last.
- Bring the fuel to the field. Driving from the field to the village or a filling station for fuel is a serious loss, especially on distant plots. Bringing the fuel to the field in a clean jerrycan with a cap is more efficient.
- Make use of return trips. Rather than going out to the field empty and coming back loaded, think about whether you could carry something on the way out too.
- Combine jobs. Group plots in the same area on the same day to cut the time the machine spends on the road.
- Choose the right day. Working when the soil is in the right condition eliminates the fuel burnt through track slip in wet soil. We have brought together everything about working on wet and sloping ground in our guide to using a tracked tractor on muddy and sloping ground.
How maintenance affects fuel: a table of losses
A poorly maintained machine burns a little more on every decare, and the difference usually builds up unnoticed. The table below shows the most common sources of loss and their symptoms:
| Source of loss | Symptom | What to do? |
|---|---|---|
| Clogged air filter | Loss of power, dark exhaust smoke | Check the filter; clean or replace it as the manual specifies |
| Slipping belt | Squealing under load, loss of traction | Adjust the tension; replace an oily or glazed belt |
| Over-tight tracks | The machine moves sluggishly, the track components run hot | Set the tension to the value in the manual |
| Blunt blades or share points | The attachment struggles to enter the soil, uneven work | Replace worn parts as a set |
| Water or dirt in the fuel | Engine misfires, power fluctuates | Check the fuel filter and water separator, and review where your fuel comes from |
| Wrong gear | The engine labours or runs at needlessly high revs | Find the right gear for the job by trial, and write it down |
| Long idling | The hours go up, the work doesn’t | Switch the engine off while waiting |
Most of the checks in the table are part of daily and weekly maintenance; you’ll find them in order in our tracked tractor maintenance checklist guide. Pay attention to the fuel itself too: clean fuel from a known source and a clean funnel are the cheapest protection against costly faults in the fuel system.
Fuel log: make the savings visible
The biggest enemy of fuel saving is that changes go unseen. A simple log solves this. At every fill-up, write the following down in a notebook or on your phone:
- Date and plot
- Job done (rotary tilling, ploughing, weed clearing, haulage)
- Area worked (decares)
- Fuel added (litres)
- Consumption per decare, plus any notes (wet soil, new blades, different gear)
After a few weeks you will see your own average for each job. When you look into the days that deviate clearly from the average, you will usually find the cause: a wet plot, a slipping belt or an unnecessary second pass.
Turning the log into costs is easy too: fuel cost per decare = litres per decare × price per litre of fuel. Use the current pump price in your area for the price per litre. Example (hypothetical figures): An improvement of 0.3 litres per decare means about 60 litres for a farm that works 200 decares a year. Do this calculation with your own area and your own improvement.
Fuel-saving checklist for the season
- I’ve measured baseline consumption for each type of job with the full-tank method.
- I work when the soil is in the right condition; I don’t burn fuel through track slip in wet soil.
- I choose the depth and number of passes according to what the job really needs.
- I’ve found the right gear for each job by trial and written it down.
- I work along the long side and keep turns and running empty to a minimum.
- I bring fuel to the field in a clean jerrycan.
- I check the air filter, belt, track tension and blades regularly.
- I switch the engine off while waiting.
- I record every fill-up and look for the cause of any deviation.
We cover fuel-saving habits for construction machinery in general in our guide to saving fuel on construction machines, and for mini excavators in particular in our guide to mini excavator fuel consumption.
Summary
- What really counts is consumption per decare, not per hour; measure it by type of job with the full-tank method.
- The QD35’s specification-table figure is 1–2 litres per decare; technique and maintenance decide which end of the range you end up at.
- Don’t labour the engine, don’t rev it needlessly high under light load, and don’t leave it idling.
- Cut the empty metres with long strips, planned turns and fuel brought to the field.
- Air filter, belt, track and blade maintenance shows up directly in your fuel use.
- Keep records; savings only last when they are visible.
You’ll find all the engine, gear and fuel figures on the QD35 tracked tractor page. Share your own fuel log with us and we’ll assess your consumption together; message us on WhatsApp.
