Automotive Fluids - Lubricating Oils & Greases, Fuels, Coolants & Brake Fluids
KEW Engineering Ltd
Additives are usually chemicals dissolved within the oil and act on the contaminants and components rather than on the oil itself. They either coat the surfaces of the components or surround the particles or droplets of acids or moisture.
These additives are typically:
Modifiers - such as Anti-Wear (AW) or animal fats as friction modifiers to
reduce friction between two components in direct contact (such as cams and
followers). Mild EP (Extreme
Pressure) additives may also be used and especially so now that the adpac
formulations are changing to reduce the levels of certain elements such as
Zinc for engines with catalytic converters.
to keep surfaces clean and often formulated with an alkaline or base
product to combat acid build up in the engines, especially so on diesel
engines, where fuel dilution and moisture can lead to Sulphuric acid. See Oil
to hold contaminants such as soot and wear debris in suspension to aid
filtering and ensure effective draining of the old oil
and rust inhibitors to protect against acid and moisture attack
to help release air bubbles quickly and prevent cavitation damage in high
pressure zones. Oil level (when
both too low or too high) generates excess foaming conditions
to slow down the oxidation rate and extend the oil life
point depressants to stop the oil going waxy or semi-solid in very cold
conditions – the additives work down to as low as -30°C
Index Improvers for Multi-grades to allow mutli-seasonal use. See
Figure 3 - Load, Friction Control and
Friction Modifiers preventing
Two similar dry surfaces in contact will experience
friction and with increased loading, seizure will result.
Wetting the surfaces with oil will reduce the friction but ultimately
seizure will still occur.
Adding Fatty Acids or oiliness agents will help, but
beyond that, AW (Anti-Wear) additives are needed, and then EP is required.
The Friction Modifiers work by modifying the component
surface making it more ductile and reducing the friction coefficient.
Think of two bars of dry soap, and then how slippery they become when
wet. AW is less aggressive in this
way than EP, only modifying the surface to a depth of less than 0.1µm as
compared to EP which works to a depth typically of 0.5µm.
AW is usually ZDDP or to give it its full name, Zinc DialkylDithioPhosphate. Owing to the use of exhaust catalytic converters (exhaust gas aftertreatment) and the environmental push to limit Zinc and Sulphur, newer oil formulations have reduced levels of Zinc. Consequently there has been some discussion to suggest that this may affect the wear rate of the flat topped cam followers used in older engine designs.
The fact is that the levels of ZDDP in modern oils are still sufficiently high enough to protect most classic engines, and today’s oils still have as much as 4 times the amount of ZDDP by comparison to oils formulated in the early 1960s when the A and B Series were first used in production cars. Whilst newer engine designs differ from older designs, the newer oil formulations more than compensate for wear protection by having differing formulations for AW protection.
All parts of the modern engine still need some AW and
mild EP protection during start-up when the engine surfaces are ‘dry’ and
speed is insufficient to achieve thick film lubrication and the crucial
separation of the components. A point to note is that some of this protection
layer is lost during a cold start and also that AW and mild EP require heat to
activate. Therefore a cold engine is
susceptible to greater wear during the warming up period, in my opinion.
For many applications Fatty Acids or Oiliness Agents
and AW are sufficient. For
extreme loading such as experienced in an axle differential, EP (Extreme
Pressure) additive is used. EP is like an AW additive, except that it is
formulated for extreme loading, and acts more aggressively on the metal
surfaces. It is often a sulphur
phosphorous base, hence the distinctive smell, and the active Sulphur may attack
yellow metals such as copper or bronze in high temperature environments.
Therefore, it is necessary to restrict its use to the differential only,
and avoid use in a gearbox with Copper based synchro-mesh rings unless otherwise
stated as ok for use by the transmission manufacturer.
Its use should also be avoided in gearboxes that use a cone/friction
clutch (Overdrive) as slippage and increased wear will result.
Ask any supplier of aftermarket additives these few questions:
Then ask yourself why:
Major lubricant companies don’t use the technology that is being claimed as a scientific breakthrough despite their multi-million dollar budgets and team of scientists all with a Ph.D.
Can you really improve on the tried and tested formulation by a little bit of brewing of different products?
If performance is such a concern, why not just buy a good oil to begin with?
oil's original additive formulation is in fact a compromise of all the needs of
the oil and the machine for which it is blended. The adpac formulation
must take into consideration all the additives that act on the surfaces and
ensure these are given due consideration for space.
By altering that balance, some of the original adpac will be excluded
from the component surface, resulting in issues like longer term corrosion and
rust, as well as potential problems with the oil such as foaming etc.
aftermarket additives are an additional form of anti-wear relying on Chlorine.
These may look impressive in the simple demonstrations given at trade
shows but like a magician, this simple test won’t let you see all that you
should be seeing. The Chlorine can
be corrosive and a potential health hazard.
The simple test rig may show evidence of removing the scars, therefore by
implication, excellent wear control and even repair of existing damage, but what
has happened to the surface profile as a result of that polishing action?
Another element of these simple demonstrations is the ability to continue
operating under increased loads – but if these high loads were to be
encountered in an engine, then the oils would have been formulated accordingly.
When one considers what a drum of this additive costs – very little –
and what they sell this additive for in little 100mL bottles – a lot - then do
the mathematics and figure out how much money is being made here, often from a
domestic garage on a typical housing estate.
forms of aftermarket additive formulation include solid lubrication such as
Molybdenum Disulphide, graphite and PTFE (or Teflon – a trademark of DuPont
and licensed for use by Interflon). In all these cases, it is a solid suspension
additive in the oil. The filters will either remove much of these solid
suspensions or the suspension will settle to the bottom of your sump.
These oil additives are possibly better suited to use in something like a
gearbox or differential. But again, care should be taken. Friction
is not always your enemy. Rolling element bearings and synchromesh rings
require some friction to ensure their successful operation. Too little friction
and the rolling elements will then slide instead of rolling, resulting in flat
spots and possible collapse of the bearing.
Lewis Research Center:
the types of bearing surface contact we have looked at, we have seen no benefit.
In some cases we have seen detrimental effect. The solids in the oil tend to
accumulate at inlets and act as a dam, which simply blocks the oil from
entering. Instead of helping, it is actually depriving parts of lubricant"
a University of Utah study:
was a pressure drop across the oil filter resulting from possible clogging of
small passageways. Oil analysis showed that iron contamination doubled after the
treatment, indicating that engine wear increased”
theory, these solids look attractive and can repair pitted surfaces on gear
teeth, but in practice they have been known to clog oil ways and filters.
of the claims look attractive, but I often see no supporting evidence save for
the anecdotal evidence given by “satisfied customers” and dubious science
lessons from fading celebrities. In fact several years ago the FCC in the US
fined one additive purveyor US$10million for false advertising. They were unable
to prove their performance claims of less wear and more reliable engine
performance compared to normal motor oil alone.
have been many independent studies on Slick 50, the most noteworthy include the
National Research Council in Canada and South – Western Research Institute
under the sponsorship of GM. None of these studies have found benefits and many
have found drawbacks. Typical drawbacks reported in the literature and users
with all aftermarket additives there are the usual problems such as:
Aftermarket additives can, and do, have their place
where used with caution for such operations as flushing, seal enhancing on a
leaking unit and perhaps improving EP performance in a gearbox, but in the main
my strategy is to buy the best oil, fluids and fuels I can justify.