“A 100-litre fuel tank on a large petrol-engine SUV now costs over R1600 to fill,” observes Hennie Botha, Key Hire Director Fleet. Botha adds – “Following on COVID-19, and as many now struggle to maintain a lifestyle, diesel, petrol and oil are highly negotiable and subject to fraud and a variety of scams.”

“Controlling fuel consumption is a multi-disciplinary task,” says Botha, continuing – “Reputable diesel engine manufacturers report that well over 60 items go into impacting fuel usage. This all ends up under the driver’s foot where roadcraft, attitude, and powertrain management play a role.”



Botha comments – “One area that is often neglected is the subject of excessive engine idling.” Here are a few reasons why engines are left idling:


  • The incorrect belief that a diesel engine must be kept warm. Modern cooling systems equipped with thermostats, viscous-coupled fans, sensors, and heat exchangers do not need to be kept idling. In Europe, where winter temperatures can run consistently below zero centigrade, the trend is towards automatic idle cut-off.
  • Driver and crew comfort can mean aircon units or heaters are left running with engine idling depending on weather conditions.
  • Leaking airbrake systems will result in falling brake pressures that need idling to maintain brake pressure – this applies particularly to trailer operations. Fix the brakes and stop the idling.

    • How much fuel does a diesel engine use on idle? Here is a formula:

  • An engine will use 10% of its displacement – engine capacity – at 650rpm per hour. Increase in rpm results in increased fuel usage.
  • For example, an 8-litre diesel engine will consume 0,8 litres/hour at idle. Two hours of idling per day equals 1,6 litres which on a year of 240 workdays turns into 384 litres diesel fuel. The inland price for 50ppm diesel fuel is R14,81 which means a year of idling only two hours per day turns into R5687. Multiply this over a fleet and idling turns into big money lost.
    • Botha concludes – “Telematics play an important role in fuel consumption reduction. Tracking driver behaviour and giving feedback is all part of the process of controlling fuel. It is all about carbon footprint, variable cost reduction and fleet discipline.”



    If you wish to discuss this or for more information, please contact Hennie Botha at hennie.botha@keygroup.co.za or at 031 713 3111.