Oil analysis — the fundamentals P.14
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QUESTIONS
O U R E X P E RT S TAC K L E
ALL YOUR QUERIES
FROM OUR READERS
We have noted colour
changes in the oils we
receive. Sometimes
the oil is light colored,
cloudy or darker, what causes
this? — William Karenga
Most oils have different colour characteristics. There are various reasons why
an oil would have a different colour from
another one.
For most of the oils made from Group I
mineral base oil, slight changes in colour
or darkness often occur due to differences in crude stock determined by the
crude source. Colour marks in mineral
oils are generally associated with sulfur
or aromatic impurities. The darker the
base oil, the more of these impurities you
usually find. Mineral oils with higher
viscosity often are characterized with
darker colours.
Certain additives can also contribute
to colour, especially those containing
sulfur. A good example is detergents
Are synthetic automotive engine oils compatible with mineral
and other synthetic
engine oils? Are they
capable to extend drain intervals?
— Peter Mulwa
Yes, synthetic oils for passenger cars and
light trucks use are fully compatible with
petroleum oil and other synthetic lubricants.
But, even though they are compatible it is
best not to mix different brands of oil.
Each brand of oil has a specific chemistry
and additive package and two different oils
mixed together may result in loss of optimal
performance as they were engineered to if
the chemistries of the oil becomes offset by
mixing with another brand of oil.
It is advisable to drain your oil completely
and charge the system with new oil to be able
to get all the benefits of the new oil.
On the issue of extending the drain
interval, some are and some are not capable.
The only way to confirm, is to check the
6
such as calcium sulfonate which can
considerably darken a finished oil.
If your lubricant supplier has made
a formulation change, this can lead to a
corresponding colour change.
It is important that lubricant suppliers
disclose planned formulation changes to
their customers in advance to avoid any
panic due to the same. If one receives an
out of norm delivery which is cloudy,
whilst previous deliveries have been clear
and bright, some common issues can be
attributed to this such as:
1. Insoluble additives (blend plant or
storage stability problems)
2. Water contamination in the oil
3. Accidental cross-mixing of lubricant
types where additives or base oils have
clashed
4. Solid impurities in the oil
5. Low cloud point (wax crystallization)
It is advisable when in doubt to contact
your lubricant supplier for clarification
and an analysis can be done to resolve
this.
.
OEM(Original Equipment Manufacturer)
specifications and the oil manufacturers
specifications. This can also be verified by oil
analysis testing at different intervals during
use which can give the estimated extended
drain interval an oil can reach.
If by-pass filtration and oil analysis is
used, then drain intervals can be extended
until the lab results indicate the oil needs to
be changed. This can be several thousands
of kilometres depending on the variables.
However, to gain a long drain interval, several
other issues need to be addressed to avoid
compromising the engin