Automotive Fluids -
Lubricating Oils & Greases, Fuels, Coolants & Brake Fluids
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Copyright 2009 |
I would like to know whether for NORMAL driving it’s worth the added expense of using semi-synthetic or synthetic oils in my modern car?If
you plan to keep your car for more than 5 years then go for best you can afford.
That means synthetic, not semi-synthetic. For
an intended ownership of 3 years or 60k miles operation, use what's recommended
and then let the next owner worry about it. Seriously,
if you plan to maintain a Full Service History by having a dealer service for a
3yr/60k ownership, then let the dealer put in what they offer; it should be the
approved oil. That said, I know one
owner of a dealer-serviced prestige German car was dumbfounded after 100k miles
and 6 yrs to find the pick-up strainer blocked with sludge.
Something is seriously wrong there and one suspects that cheap oil was
used but expensive oil paid for in the servicing bill. Going
for fully synthetic will mean dumping oil at 12 to 15k miles depending on your
service schedule, but that oil may still be good for another 10k if you do a lot
of motorway miles at legal speeds. The upside is that if you plan to run the car
for the next ten years then buy the fully synthetic, it will help ensure optimum
oil performance between services. Don’t
forget to use good quality fuel to keep the injectors and engine clean. I
don’t like to be drawn into recommending brands so don’t ask. I do occasional track days, too, in my car what should I use?There
are a couple of other smaller specialist oil manufacturers who use purer base
stocks that are less susceptible to shearing and provide greater film strength.
These are proven case studies, the motorsport people use names like Motul,
Redline and Royal Purple and independent assessment has shown better wear
protection than even some of the best major brand oils. On
a classic it may pay of course to just change the oil before and after that
track day session. Are frequent oil changes better?Many
people still believe that frequent oil changes are the best way to look after an
engine, which is true up to a point if you do the oil change while the oil is
still warm as it drains out more of the solids and wear debris material from the
system than it would when cold. If
you are looking to extend the oil drain interval, then a fully synthetic is a
better choice to minimise harm from premature oil failure. Standard mineral and
semi synthetic oils offer satisfactory protection but be warned that they do not
always last the service interval (depending on your style of driving). What type of oil does the factory use?This
will vary between manufacturers and oil companies are keen to get this type of
key account. In some cases the
choice of oil is based on tests, in other cases it is purely a commercial
decision. Check with the vehicle supplier what is recommended by the
manufacturer. In
the case of your classic any oil you use now will be better than what the
factory used in 1960.
Why does my oil go black just after I change it?Firstly, engine oil is designed to
hold very fine particles of material in suspension.
It has a dispersancy package that keeps the particles finely suspended
and stops them clumping together to form larger. more abrasive and harmful
particles. These particles maybe
fine wear debris from the component surfaces, or possibly ‘soot’, very fine
carbon particles from the combustion chamber that get passed the piston rings
through blow-by on the combustion stroke. If
you look closely at the oil, you can sometimes just about discern the very fine
particulate in the oil. In some cases the oil, when old, may actually feel
gritty to the touch. Diesels produce a lot of soot
particulate compared to petrol engines and so as a rule, diesel engine oils have
a higher level of dispersancy than petrol engine oils.
In more recent years, Exhaust Gas Recirculation has become normal on many
diesel engines and so there is a tendency for more soot to appear in the oil,
because as unburnt fuel is recirculated back into the inlet from the exhaust,
some soot particulate is dragged through, too.
The oil going black was always a sure
sign that the oil had a good detergency and dispersancy package.
However, on newer engines with tighter clearances and more efficient
combustion owing to the ECU, and partly thanks to modern oils, there is less of
this effect occurring so it will stay clearer for longer.
My engine is modified, should I deal with it differently?Your
engine will be stressed a little more than the standard anticipated design usage
and may generate more heat. For safety, extended reliability and reduced wear
rate, superior oil should be used to counter the effects of the modification
work. Essentially, the higher film
strength of a synthetic will reduce the impact of the increased loading from the
extra modifications. Film
strength is the ability of the oil to support a load without metal-to-metal
contact between the components. Film
strength at the bearing is dependent on the oil's capability to resist shear at
the bearing. Some of the best oils
are expensive but do offer significant protection despite being a lower
viscosity. This lower viscosity reduces friction from the oil at the bearing
thus allowing more power to be transmitted to the drive-train. This kind of oil
finds favour with motorsport people who are seeing very good engine life and oil
life during a hard racing season. Another
reason to use a synthetic in a modified car is to allow for increase heat
build-up when the car is used harder, as synthetics resist heat degradation
better. Should I keep
this oil in until the next service schedule and just top it up for now?
In another words, can
I mix oils?
Being
pragmatic, I say better to have the right level of oil than worry about the
mixing effects over time. However,
always try to stick with one brand as cross-mixing of oils can impair additive
performance. Generally, though, there will be no adverse effects from
cross-mixing brands of oils.
Why is Idling bad for my engine?Particularly
on diesels, idling will not allow the full combustion to take place, so wet fuel
remains in the cylinder and starts to run down the bores. This will reduce the
wear control from the oil splashed up onto the cylinder walls, and further, will
accumulate in the oil, lowering the viscosity and reduce additive effectiveness
such as the dispersancy additive, causing larger particles to increase wear
rates. In some cases the dilution can become dangerously high (>5%).
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