OIL SYSTEMS GO !
Many motorists take the view that one oil is much the same as another, so why spend more than the minimum when purchasing? Well, although oils may look and feel very similar, their specifications are as wide and varied as the number of brands on the market. The bottom line is that filling your engine with a poor quality or incorrect specification of oil will drastically reduce its service life, in some cases within just a few miles! The British Lubricants Federation issues a guidance leaflet with this clear message:
"Choosing the correct engine oil can save motorists the price of many gallons of fuel a year in addition to prolonging service life"
So what is so special about oil? To understand this you must first recognise that lubricating oil, apart from reducing wear and friction, provides four additional and very important functions:
1) it acts as a cooling medium;
2) it keeps the internal components clean;
3) it prevents corrosion;
4) it reduces noise.
So how do you tell the difference? Oil specification is determined by two criteria namely Viscosity (or thickness) and Performance (or quality). We shall deal with these separately:
Viscosity is simply the 'thickness' of oil. Most engine wear occurs during the critical moments following a cold start. High viscosity (thicker) oils circulate slower than low viscosity oils and the colder the oil, the thicker it will be. The Society of Automotive Engineers (SAE) classification system establishes the viscosity characteristics for the lubricating oil industry. All multi-
Performance standards are currently laid down for three automotive engine groups namely: petrol light duty diesel, and heavy-
Figure 2 illustrates the improvements made to oil quality since the original 'SA' standard was introduced and how significantly oil performance has advanced over the last 20 years. In 1996 a new European standard was introduced (ACEA) to improve the clarity of test programmes and assert minimum quality standards from the oil blenders. Below are listed the three specifications for petrol engines (A1;A2;A3) which are then suffixed by the year the standard was changed.
ACEA SPECIFICATIONS FOR PETROL ENGINES:
Regardless of the age of an engine, any newer specification can be used providing the viscosity is correct. However, when you choose to use a higher specification oil the oil change period must never be extended. Nearly all the oil sold will have me API and/or ACEA classification printed on the container and, unless it is a very old vehicle, we would not advise using any oil below API 'SF quality (all ACEA standards meet or exceed API 'SF'). If there is no API or ACEA classification on the container -
Although commanding a premium price these do offer excellent value for money through 'state of the art' technology. Synthetic oils offer advantages in most engines, particularly in respect of performance under extreme service conditions such as are encountered in turbo-
Purchasing synthetic oil however, is not always a simple procedure since there are several differing interpretations of the word synthetic and also the availability of 'semi' or 'partially' synthetic oils. These semi or partially synthetic oils are generally a mixture of conventional mineral oils with an undefined proportion of synthetic oils which can offer some of the advantages of 100% synthetics but never the full technical advantages Whilst partial synthetics are excellent oils at a lower cost, if you want the very best engine protection your money can buy then insist on Fully or 100% synthetic -
Some final tips on oil changing:
Frank Sherlock -
Graham Lord -
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