Fuel Efficient Testing For Commercial Vehicles

Why Fuel Efficient Testing is required?

In commercial vehicle segment, the major part of the business operating economics is depending on factor like;

  • Fuel cost
  • Tyre cost
  • Vehicle maintenance cost
  • Revenue license and insurance

Fuel is takes almost 60% – 65% cost from overall vehicle expenses. With that scenario, vehicles   owners are always concern about the fuel consumption.

 Things to know about Fuel economy

  • Aerodynamic is playing key role with fuel economy. 2% reduction of aerodynamic drag will improve fuel economy by 1%.
  • Ribbed tires will improve the fuel economy than lugged tires (2% to 4 %)
  • 55 kmph is the perfect speed for fuel economy. Every 1 kmph, above 55 kmph will decrease the fuel economy by 0.04 kmpl.
  • Used lug tires will give better fuel economy than new lug tires
  • Every 10 psi under inflated tire will reduce fuel economy by 1%
  • Efficient driver can improve the fuel economy by 30% than new driver
  • Tyre’s will affect the fuel economy in less than 50 kmph
  • Aerodynamic will affect the fuel economy above 50 kmph
  • Idle time increases the fuel economy. Try to minimize idle time.

 Key factors which relates to fuel economy


  • Aerodynamic
  • The gap between Tractor and Trailer
  • Proper lubrication to the vehicle rotatory parts
  • Engine idle rpm
  • Load on axle
  • Type of loading material
  • Driving techniques
  • Vehicle Speed
  • Load and loading condition
  • Tyre Pressure
  • Tire Construction
  • Ambient temperature
  • Tire and Axle alignment
  • Engine condition
  • Road condition
  • Road gradient
  • Climate condition
  • Wind direction

Fuel economy testing are not always giving proper end result due to some gaps;

  • Basically customers are used vehicle with overloaded.
  • Not proper maintain log book for vehicles
  • Customer fuel economy expectation is based on their business, not as per the vehicle application.


To avoid those outcomes, standard operation procedure must follow to conduct the fuel economy test.

Fuel Tank Full

Standard Operation Procedure

 Understanding with the customer

  • Target FE  value should be based on Logbook data ( in case Logbook is not available  similar configuration competition vehicle is suggested)
  • Fuel top up points ‐ The fuel filling point must be decided before start of
  • Payload ‐ The pay load should be pre-decided, recommendation is for rated payload to 10% overload.
  • Discuss with customer for trial report sharing methodology


How To Fill The Fuel Correctly For Fuel Testing

 Filling fuel is one of most important activity in Fuel economy test.

    • Fueling must done at authorized fueling station only
    • Shut down the engine at least 15 min for cooling the fuel system before fill the fuel
    •  Diesel must fill when the ambient temperature moderately cool.
    •  Filling should have done by medium speed with fueling pump.
    •  Vehicle should be parked in plain ground.
    •   Wait some time for escape trap air
    •  Filling cap must properly fix to fuel neck

Best Driving Practice:


Best driving practices can increase the fuel economy.

  • High average vehicle speed with minimum time spent at maximum vehicle
  • High percent trip distance in top gear (90+ % recommended)
  • High percent distance in cruise
  • Minimum percent idle/PTO operation
  • Minimum service brake activity
  • Avoid aggressive overtaking, which impacts Fuel Economy
  • Each Gear change is advised below / around engine rpm 1800
  • Moving from 5th to 6th may use 1600 rpm is recommended
  • Moving from 1st to 2nd may use max 1800 rpm is recommended

Calculating Procedure

After   complete drive with actual load condition and the actual customer route.

  • Refuel the vehicle with same procedure
  • Divide the total driven mileage by fuel quantity.
  • Average fuel consumption can be get through that procedure

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