Ask the Expert
Ask the Expert

Ask the Expert

Jason Hurdis, Global Construction & Infrastructure Division (GCI) Global Market Professional


Jason, fuel expenses can account for 30-50% of a machine’s operating costs. What issues can be addressed to reduce those costs?

Fuel efficiency does incorporate the amount of fuel burned, but its final value is dependent on several factors both machine and non-machine influencers.  These factors, or fuel efficiency influencers, can be categorized as follow:

  1. Idle Time – how long a machine runs without performing any value added work.
  2. Operator Technique – how the operator controls the machines, engine speed, hydraulic powers, rimpull and loading.
  3. Jobsite set-up – how the job site is laid out and machine flow throughout the job site to minimize wasted movements
  4. Equipment selection & configuration – the right machine for the job or task. Too small increases fuel burn and reduces operator effectiveness. Too large and fuel consumption increases without optimum productivity match
  5. Technology – both on and off board technology such as machine idle management technologies, off board measurement to determine ‘normal’ or ‘typical’ operation metrics

You believe the easiest way for governmental agencies to reduce fuel costs is to reduce idle time. What needs to be done to cut down idle time?

Equipment idle time is one of the largest and generally the most misunderstood influences to fuel efficiency. Idle time is defined as fuel being consumed with no work or productivity.

Idle time in construction equipment applications is impossible to avoid considering equipment warm up requirements, shut down requirements and various application segments. Industry studies show construction equipment idle time can be as much as 40-50% of total operation time. Chart 1 is a simple example of idle time cost.

 

Save on Fuel

See how fuel fundamentals will help you cut costs, increase productivity and get more work from every tank.

Get Info
Motor Graders
Motor Graders
Idle Time Impact

Operating Hours
per Year
Idle Time
Percentage
Idle Hours
Per Year
Annual Cost
of Idle Time
Five Year
Cumulative Costs

2,000 20% 400 $1,560 $7,800
2,000 25% 500 $1,950 $9,750
2,000 30% 600 $2,340 $11,700
2,000 35% 700 $2,730 $13,650
2,000 40% 800 $3,120 $15,600
2,000 45% 900 $3,510 $17,550

 

Fuel = $3.80 / gal
Idle Fuel burn = 1.0 gph

 

As shown in Chart 1, idle time and fuel used at idle can increase operational costs. The above Chart does not include secondary idle time costs such as; engine wear, fuel system wear, lower trade values, shortened oil change durations, reduction in equipment warranty hours and increased repair costs.

It is obvious idle time has a direct impact on fuel consumption. In fact, when idle time is reduced, hourly fuel consumption is actually increased. This relationship is often confusing to users as the general thought is if the equipment is idling less, than the hourly fuel consumption should decrease, not increase. This phenomenon is best explained by understanding the relationship between idle time, working time, productivity, fuel consumption and fuel efficiency.

Chart 2 shows the relationship between idle time reduction, hourly fuel consumption, production and fuel efficiency. A 10 ton payload wheel loader was used as the test case. In this test case, as the idle percentage is reduced, the working percentage, productivity (tons/hour) and hourly fuel consumption (liter/hour) increase. As a result, the equipment is moving more material for every hour and liter consumed directly improving fuel efficiency.

 

Chart 2 - 10 Ton Wheel Loader-Idle Time Impact
 
Production
(Tons/Hour)
Idling
(Liters/Hour)
Working
(Liters/Hour)
Idling
(%)
Working
(%)
Fuel Consumption
(Liter/Hour)
Fuel Efficiency
(Tons/Liter)
Fiuel Efficiency
(Index)

250 4.1 27.7 50% 50%
15.9 15.7
100
275 4.1 27.7 45% 55%
17.1 16.1
102
300 4.1 27.7 40% 60%
18.3 16.4
104
325 4.1 27.7 35% 65%
19.4 16.7
106
350 4.1 27.7 30% 70%
20.6 17.0
108
375 4.1 27.7 25% 75%
21.8 17.2
109
400 4.1 27.7 20% 80%
23.0 17.4 111
425 4.1 27.7 15% 85% 24.2 17.6 112
450 4.1 27.7 10% 90% 25.3 17.8 113

 

Further study of Chart 2, finds a 10% reduction in idle percentage from 50% idling improves fuel efficiency by 4%, a 20% reduction in idle results in an 8% fuel efficiency improvement and a reduction of 40% increases fuel efficiency by 13%.

While some equipment idle time is unavoidable, it can still be controlled or minimized in construction equipment applications. The following are effective methods to reduce idle time.

  1. Education – Reviewing fuel consumption data and fuel costs with employees helps educate them on idling effects to the equipment, overall operation, environmental stewardship and company profits.
  2. Limit warm up time – Equipment warm up time at start of shift varies by ambient conditions, but a rule of thumb from the Environmental Protection Agency (EPA) indicates warm up times can be limited to 3 to 5 minutes.
  3. Implement 5 minute idle rule – If equipment idles for more than 5 minutes, shut it down to save fuel. Restarting equipment uses less fuel than idling considering most construction equipment consumes an average of one gallon per hour at idle. Most construction equipment manufacturers offer as standard or option attachments shut down timers that automatically shut off machines after five minutes or other user defined time periods.
  4. Limit cool down time – Equipment should be idled at end of shift to allow turbochargers and emission systems to cool and purge. As another general rule, idling for two minutes at the end of the shift will allow most equipment to reach optimum shutdown temperatures. Newer construction equipment has automatic shutdown features that control this time and process for the user.
  5. Idle management systems – Some construction equipment is equipped with ‘auto-idle’ or ‘engine idle management’ systems. These systems monitor equipment parameters and automatically reduce engine rpm to idle rpm or below normal machine idle rpm. Using these systems can reduce idle fuel consumption to less than 1 gallon per hour.
  6. Breaks and lunch – Studies and observations indicate construction equipment is left idling over breaks or lunch periods. The most frequent reason stated by construction equipment operators for doing this is to keep cab environment at temperature, whether warm or cool. Systems such as engine off cab heaters and coolers can reduce the “need” to idle over breaks and lunch. Operator education and layout of break/lunch areas to production areas can be helpful as well.
  7. Monitoring asset utilization – Best practice today includes the using telematics for monitoring equipment and utilization to benchmark and identify opportunities to reduce idling time and enhance the fleet utilization.

 

What technology on Cat® machines can also help operators burn less fuel?

Technology on Cat machines encompasses both telematics and equipment technologies. Each is equally important to construction equipment fuel efficiency, and as such, neither should be overlooked.

  1. Telematics – Telematics can be broken down into two sections: off-board and on-board. Off-board telematics, such as VisionLink™, provides individual machine or fleet information to site personnel. This is important for two basic reasons. First, VisionLink™ telematics provides site personnel with fuel information such as idle time fuel consumption, working time fuel consumption and fuel efficiency without additional labor that would be required to obtain this data via on-site measurement. Second, having this information allows site personnel to better understand their operations and make continuous analysis of individual machines, operators, and job site setup to improve and sustain fuel efficiency.
        On-board or on-machine telematics are machine monitoring systems and displays providing the operator with real-time information such as productivity, fuel consumption, idle time, and fuel efficiency.  This information allows the operator to adjust the operating technique or machine to improve fuel efficiency in real time. The operator can also use this information with site management to assist in job site improvements or identify issues that may be affecting fuel efficiency.
  2. Machine technology – Advancements in construction equipment design and development have been rapid in the last five years. Several Caterpillar engines and machine platforms are now designed to deliver full power at lower RPMs which reduces fuel consumption and emission packages. As example, Tier IV final engines allow instantaneously adjustments to machine performance and fuel consumption based on numerous machine inputs. Some manufacturers have reduced engine displacements to enhance the optimum performance of the engine and deliver fuel consumption reductions without any reductions in productivity.
  3. Advanced technologies- Advanced Cat machine technologies such as electric drive, hydrostatic or continuously variable transmissions have been introduced on wheel loader and track-type tractor platforms. These machine technologies are creating double-digit fuel consumption reduction with productivity levels equal to or greater than standard configured models in the same size and machine class. Several of these technologies also improve the operator technique by automatically adjusting performance or transmission settings.
  4. “Add-on” technologies- “add-on” technologies such as Cat GRADE technologies and Cat PAYLOAD technologies can improve fuel efficiency. GRADE technologies improve operator efficiencies and reduce unnecessary idle and fuel consumption. PAYLOAD, like Caterpillar Production Measurement, improve production, reduce idle time, reduce fuel consumption and improve operator efficiencies.