by Dave Scott, independent author; information supplied by WearCheck

Say ‘dipstick’ and any driver’s mind flies towards an engine oil dipstick – especially older truck models that are not electronically equipped with sump level sensors and instrument panel signals. But modern trucks come standard with other fluid dipsticks as well, and that is where it all begins.

A driver’s daily check sheet will include engine oil levels. But, unless the check is specific and limited to the engine only with training on how and when to read the dipstick, there is a danger that an ‘enthusiastic’ driver starts checking all the other dipstick levels that are best left to workshop technicians.

Power steering, torque convertor automatic transmissions and automated manual transmission (AMT) viscous couplings all require top-up techniques at operating temperatures with absolute cleanliness. Also, some systems – such as automatic gearboxes – require the lubricant level to be checked while the engine is running at idle. And then all components outside of the engine require very specific lubricants totally different to engine lube specs.

Early morning start-up audit

Start-up and checking procedures are often executed in poor lighting conditions and pre-dawn, without a torch. This makes reading an engine dipstick a hit-and-miss procedure, where the faulty perception exists that it is better to err on the side of overfilling. The hit-and-miss problem is compounded with returning and inserting the dipstick in the dark and missing the dipstick seating orifice – the bottom of the dipstick gets jammed into grinding material collected around the dipstick entry point.

The accumulated contamination is then inserted into the engine to initiate engine wear and premature failure – a disaster!

It sounds too basic to be true, but engine lube levels must be checked when a vehicle is on a level surface.

Dipstick procedures must be cold checks

Top-up oils are most often stored at the fuel pump, which entails a vehicle movement to the fuel pump before checking the dipstick – oil levels should be checked before engine start-up. By the time the vehicle arrives for refuelling, the engine has warmed up and oil is in the cylinder head and other galleys to give a false dipstick reading. A hot truck engine cylinder head can hold many litres of lubricant when switched off – in some cases the recommended waiting period prior to checking the engine sump dipstick is at least 10 to 30 minutes, depending on engine design and sump capacity. 

Case study: The dipstick that was too short

A new truck recorded excessive oil consumption. Before the engine was going to be stripped down, a visiting service manager asked for a spare dipstick from the parts division for comparison to the dipstick already in the engine that was used as the measuring device for excessive oil consumption. The wrong dipstick was present in the motor and, being too short, the engine was overfilled every time while blowing out the excess oil on every trip – the correct dipstick solved the problem without a costly, and fruitless, engine teardown.

The overlooked engine breather’s role

A rotating crankshaft, churning the lubricant in the sump, creates a heavy oil mist that leaves through a breather that, on modern engines, exits into the airflow before the turbocharger. If it entered after the turbocharger, the turbo would pressurise the sump! Abnormal lubricant volume in the turbo will deposit on the impeller blades, unbalancing the turbo and resulting in failure. Extra oil can also partially block the intercooler, leading to lack of power and increased fuel consumption. Excessive lubricant can also enter the combustion chamber where it burns, and the engine can run on or run away. Worse still, the excess pressure created can blow an oil seal.

Disaster warning: an increasing engine oil dipstick level

In addition, drivers and technicians are not trained in tracking the severe warning signal that an increase in dipstick level provides. Is this noticed and reported? When this is noticed and recorded, action must be taken to determine the root cause of an elevated level. Is it due to the over-filling of the sump with engine lubricant or is it fuel or coolant dilution? In which case, drain the sump and determine the problem.

Halfway is good

Drivers must be trained to read dipstick levels. An increasing level of oil means whoa! Watch out! But halfway between the bottom and top marker on the dipstick is perfectly acceptable. What is the fill-amount between the bottom and top markers? What is not desirable is several half-full containers lying around collecting dust and waiting to top up half-full engine sumps. The gap between bottom and top must be managed.

Distance is not a yardstick

A truck diesel engine will consume oil, but in relation to how hard the engine works and fuel consumption – not the distance the wheels have rolled. The common mistake is to establish a ratio of oil consumption to kilometres travelled per km. But (a very big “but”), 100 km in Lesotho is totally different to 100 km in the north-eastern Free State.

An abnormal load running at a gross combination mass (GCM) of 100 tons will use far more oil than a seven-axle interlink running at a 56 t GCM for the identical distance travelled. Variance in dipstick readings is relevant to fuel consumption and not distance. The most accurate ratio is a percentage of fuel consumption – a general figure across the board is around 0,6% of total fuel consumption.

Exceeding a 1% benchmark on a truck means there’s something seriously wrong mechanically, or, either negligent dipstick-level reading, or fraudulent ‘skimming’ is occurring, such as:

• Deliberate over-filling – to increase lubricant turnover

• False reading of dipstick levels to ‘skim’ the extra lubricant left when a dipstick indicates the correct level

Conclusion: Measure to manage

The priority is to establish an oil consumption database that tracks top-up lube used against individual vehicles – this will also provide a running cumulative fleet total.

Here is an outline for a plan to become operationally competent:

• Draft or update a lubrication policy in which top-up features, with its own standard operating procedures (SOPs)

• Arrive at individual and total fleet ratios of top-up to fuel consumed

• Establish benchmark averages and trends – start with a ratio of 0,6% and manage by exception. An average that exceeds 1% needs serious investigation

• Write dipstick management into a job description – who will champion this cause?

• Clean up all lube equipment – go on a contamination hunt and implement proper storage of cleaning material

• Make everyone aware of the environmental impact of dipstick and top-up control

• Get lubrication reports into the monthly management operation accounts.

Contact WearCheck, support@wearcheck.co.za, www.wearcheck.co.za