Litres per hour alone is not a measure of efficiency
When comparing excavator and loader fuel consumption, L/h alone is not enough: the same value can come from a different job, a different load and a different idle share. For a fair comparison, the same machine group, the same type of work and the same period are chosen, idle time is separated, and where possible consumption is divided by the amount of work done (L/m³, L/tonne). The L/h of a crawler excavator and a wheeled loader, on the other hand, cannot be compared directly; the work the two do in an hour is different.
The consumption ranges in manufacturers' performance brochures are given by load factor. In other words, there is no single L/h for the same machine, but a range that moves with the load. The value on site tells you where in that range the machine was working; to say whether the machine is good or bad, the load must first be fixed.
Seven factors that move L/h
Each of the factors below changes the L/h value independently of the machine. Before making a comparison, mark which of them are the same on both sides; those that are not the same are either split into separate groups or taken into account.
Factors that move L/h and how to separate them
| Factor | How it affects L/h | How to separate it |
|---|---|---|
| Type of work | Digging, loading, breaking with a breaker and grading draw different amounts of fuel on the same machine | Take the type of work from the site manager's job record and compare the types separately |
| Load factor | Consumption rises as the engine works closer to full load | Compare under the same material and the same loading conditions |
| Idle share | The engine runs but no work is done; the hour meter runs, little fuel flows and L/h falls | Measure idle hours separately; if not available, note them separately from the operator's and site manager's estimate |
| Working mode | Modes such as power or economy produce different consumption on the same job | Write the mode choice in the record note and make the comparison in the same mode |
| Attachment | A breaker, a different bucket type or bucket width changes the load | Record attachment changes with their date and separate before and after the change |
| Ground and material | Compact ground, rock, wet clay and material density increase consumption | Stay in the same pit or the same material group |
| Operator | A different operator's habits on the same machine change consumption | Combine the operator assignment with the record and look by shift |
How idle time makes L/h deceptive
In the same group, that is 20-25 tonne crawler excavators, two machines worked for a week on the same digging in the same pit. The values are examples, not manufacturer data. For both, 16 litres per working hour under load and 3 litres per hour at idle were assumed.
In L/h, machine B appears to burn 21 percent less ((12.1 − 9.5) / 12.1). Looking at fuel per job, A uses 9 percent less ((0.238 − 0.216) / 0.238). Half of B's hours are spent at idle: its L/h is low, but to do the same digging it spends more hours and more fuel. What we have here is not a fuel problem but a finding about work organization; waiting for trucks or missing preparation may have kept the machine idle.
Same class, same job: one week of sample records
| Measure | Machine A | Machine B |
|---|---|---|
| Engine hours | 50 | 50 |
| Working under load / idle | 35 hours / 15 hours | 25 hours / 25 hours |
| Fuel | 35 × 16 + 15 × 3 = 605 L | 25 × 16 + 25 × 3 = 475 L |
| L/h | 12.1 | 9.5 |
| Volume excavated | 2,800 m³ | 2,000 m³ |
| L/m³ | 0.216 | 0.238 |
Not comparing a crawler excavator and a wheeled loader by L/h
A crawler excavator mostly stays in place and digs, swings and dumps; most of the fuel goes to hydraulic work. A wheeled loader picks up material, carries it, returns and dumps; its fuel varies with movement, distance and ground resistance. The work cycle within an hour is not the same on the two machines, and the product they measure is also different: one gives the volume excavated, the other the load carried. Putting two L/h figures side by side is comparing the hours of two different jobs.
The comparison only makes sense at the point where the two are really doing the same job; for example, loading trucks at a stockpile. In the example below, the loader comes out 23 percent higher than the excavator in L/h (16 / 13) and 23 percent lower in L/tonne (0.10 / 0.13 = 0.77). This is not a ranking claim; if the material is compact or the haul distance is long, the opposite can happen too. But the example shows that the unit in which the decision is made can reverse the ranking.
Same job, loading from a stockpile onto trucks: 40-hour sample record
| Measure | Crawler excavator | Wheeled loader |
|---|---|---|
| Duration | 40 hours | 40 hours |
| Fuel | 520 L | 640 L |
| L/h | 13 | 16 |
| Material loaded | 4,000 tonnes | 6,400 tonnes |
| L/tonne | 0.13 | 0.10 |
Five steps of a fair comparison
Normalizing means bringing the two numbers to be compared to the same conditions. The order is as follows:
- Choose the same machine group: keep 20-25 t crawler excavators and wheeled loaders in separate groups. Defining the group narrowly makes the comparison fair.
- Take the same type of work and the same period: do not compare a digging week with a loading week.
- Use the average of several refills instead of a single refill; a single refill misleads if the tank was under-filled or a previous record was not entered.
- Separate idle time: write the hours worked under load and the idle hours separately. If your telemetry provider gives an idle field, take it from there; if not, take it from the operator's and site manager's notes.
- Where possible, divide consumption by the amount of work: L/m³ or L/tonne.
What data L/m³ and L/tonne are calculated with
For L/m³, the numerator is the fuel in the period and the denominator is the volume of work done in the same period. The volume is taken from the excavation quantity survey, the progress payment table, or the number of trucks multiplied by the body volume. For L/tonne, the denominator is the total tonnage on the weighbridge tickets. In both calculations, the amount of work and the fuel must belong to the same machine and the same period; if several machines work on the same job, you cannot split the work by machine, so calculate by group. Do not mix bank volume with loose volume either: the excavation survey is often in bank volume and the truck body in loose volume, and the same soil gives a different figure in each.
Which comparison answers which question
There are four types of comparison and each answers a separate question. Choosing the wrong comparison produces a result that looks right but misleads: first look at the machine's own history, then step up to the group; fuel per job comes into play in decisions such as method and machine choice.
Types of comparison, the question each answers and its limit
| Comparison | Question it answers | Limit |
|---|---|---|
| The machine's own history (for example the last 90 days) | Has this machine's consumption got worse? | If the type of work or the attachment has changed, the old band no longer applies |
| Same group, same type of work | Is this machine working outside its group? | There may be differences in age and working conditions within the group |
| Fuel per job (L/m³, L/tonne) | Which machine or method does the same job with less fuel? | Work quantity data is needed; the fuel record alone is not enough |
| L/h of different groups | Gives a solid answer to no question | The work the two machines do per hour is different |
The order for questioning a difference found in the comparison
When a machine falls outside its own band or its group, the first job is not to blame but to rule out record errors. The basis of deviation analysis is explained in the deviation guide; here is only the order specific to comparison.
- Meter error: the divisor of L/h is the meter. The meter may have been reset, hours may not have been entered, or the daily total and the engine hours may not agree; the sources are compared in the working hours guide.
- A refill recorded against the wrong machine: if the deviations of two machines are in opposite directions (one high, the other low) and their total is normal, the refill record has been mixed up; check the machine codes.
- A change of work: a new type of work, attachment, ground or shift pattern. This check is quick, and if an explanation is found the difference is legitimate; it should be done before looking for leakage.
- Fuel leakage (loss): after the above are eliminated, the tank, distribution and machine records are compared for the same period.
The records the comparison rests on in Axis
Reper Axis compares L/h with the machine's own 90-day history and with the same machine group, and flags unusual consumption. The machine group is defined in the company, for example crawler excavator 20-25 t; keeping the group this narrow makes the comparison fair. L/m³ and L/tonne, on the other hand, are outside this comparison because the amount of work is not in the fuel record; you divide the share yourself in your own table using quantity survey or weighbridge data.
Refill data comes from the following sources in order. If there is fuel automation, it sends refills with an API key. If there is no automation, the distribution list is imported in bulk with Excel. If neither exists, the QR code refuelling form is used as a fallback. On supported connections, telemetry consumption is compared with refills and a notification arrives when the deviation threshold is exceeded; the scope is verified in the technical discovery. The screen and outputs of the fuel records are described on the fuel management page.
