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Saturday, 27 August 2011

Why use synthetic motor oil?

Image: domdeen /
In any group of petrol heads the conversation will invariably turn to engine oils, engine oil price and the inevitable question as to why use synthetic motor oil?
Let’s ignore engine oil price for a moment and examine the performance of full synthetic engine oil. To keep this article brief I’ll focus on full synthetic motor oil, API Group V, as opposed to semi synthetic oil.
Synthetic motor oil is specifically blended to meet the operating requirements of the ever evolving engine. The following properties are common in
modern full synthetic engine oil:
1)    Sophisticated friction modifiers reduce energy sapping friction. This not only increases power output, but also reduces fuel consumption and can also reduce operating temperature.
2)    Because synthetic motor oil is engineered to be thermally stable, and utilises superior anti oxidation technology (over mineral engine oils), varnish build up is reduced. This keeps the internals of the engine relatively clean and reduces the sludge build up that plagued vehicles operating in heavy traffic conditions in cold climates.
•    As Turbo chargers become more durable (Largely thanks to the strides made in synthetic motor oil) more OEM’s are opting to fit these to improve engine efficiency. The reluctance to fit turbo chargers on “everyday” vehicles has largely revolved around the perception that turbo chargers were unreliable.
•    When one considers the environment that a turbo charger operates in – turbines spinning up to 200,000 RPM and housings reaching surface temperatures of 900 deg. C it’s quite obvious that mineral engine oils (Even highly refined semi synthetic oil) would be hard pressed to cope. The problem with the Turbo, is that when the engine is shut down temperatures rise rapidly, while at the same time oil circulation (That also cools the bearings) ceases. At this point it’s common for mineral oils to carburise. These diamond hard particles then act as a grinding paste on the bearings, resulting in premature failure! Fully synthetic motor oil has been proven to extend the life of the Turbo.
3)    In theory using synthetic motor oil can also extend oil-change intervals. I say in theory, merely because technically synthetic motor oil can comfortably cope with intervals of up to 40,000 km’s, although OEM warranty and service interval contracts will not allow this. Of course if you’re using synthetic motor oil in an out of warranty vehicle you can decide if you’d like to extend intervals.
•    Another reason why extended synthetic motor oil change intervals may be undesirable, relates to dirt ingress through the air filter element. Typically a new element, filters +10 micron (About the cross section of a human hair), however as the element becomes clogged with dirt the vacuum increases, resulting in larger particles being sucked into the engine. Unfortunately even the best synthetic motor oil can’t do anything about the damage this can cause.
There’s no doubt that synthetic motor oil out performs crude based engine oils, and with the engine oil price difference between the two reducing the smart choice is probably a fully synthetic motor oil.