Page 64 - Energize October 2022

TECHNICAL

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 56t GCM for the identical distance travelled.
Figure 3: Full and low marks Variance in dipstick readings is relevant to fuel consumption
and not distance. The most accurate ratio is a percentage of fuel
on the impeller blades, unbalancing the turbo and resulting in consumption – a general figure across the board is around 0,6%
failure. Extra oil can also partially block the intercooler, leading of total fuel consumption.
to lack of power and increased fuel consumption. Excessive
lubricant can also enter the combustion chamber where it burns, Exceeding a 1% benchmark on a truck means there’s something
and the engine can run on or run away. Worse still, the excess seriously wrong mechanically, or, either negligent dipstick-level
pressure created can blow an oil seal. reading, or fraudulent ‘skimming’ is occurring, such as:
• Deliberate over-filling – to increase lubricant turnover.
Disaster warning: an increasing engine oil • False reading of dipstick levels to ‘skim’ the extra lubricant
dipstick level left when a dipstick indicates the correct level.
In addition, drivers and technicians are not trained in tracking
the severe warning signal that an increase in dipstick level Bulk fuel storage dipsticks
provides. Is this noticed and reported? When this is noticed and One overlooked dipstick is that which measures bulk fuel storage
recorded, action must be taken to determine the root cause of levels. Fleet audits reveal the bulk fuel tank dipstick just lying
an elevated level. Is it due to the over-filling of the sump with on the workshop floor or even left outside in the yard. This is
engine lubricant or is it fuel or coolant dilution? In which case, yet another source of contamination unconsciously introduced
drain the sump and determine the problem. into the fuel tank during bulk fuel measurements. Modern
common-rail diesel engine injectors operating over 2500 bar
Halfway is good are sensitive to particles over four micron – every effort must
Drivers must be trained to read dipstick levels. An increasing be made to avoid contamination. The advice below comes from
level of oil means whoa! Watch out! But halfway between the Lubrication Excellence/Reliability World 2005 Conference
the bottom and top marker on the dipstick is perfectly Proceedings. It is an excerpt from “Using oil analysis as a root
cause analysis tool”.

What is a lubrication failure?
The term “lubrication failure” is widely abused in industry.
It is generally applied to any failure in which the lubricant
is suspected. In some cases, it is assigned as a matter of
convenience simply because no other cause was readily
revealed. Ineffective lubrication often lies at the root of
mechanical wear and failure, but one must develop a
clearer understanding of lubrication failures and investigate
them individually. There is no single definition for
lubrication failure, rather, multiple possible failures with
multiple possible causes. Evaluate each significant failure
independently of previous failures, avoiding the temptation
to casually apply the scenario from a previous failure to the
Figure 4: Bulk fuel dip water test current one.

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