Engine oil viscosity
Viscosity refers to the degree of fluidity of engine oil. The fluidity of oil varies with temperature. As the temperature increases, it liquefies. This affects the durability and resistance of the lubricating film. When cold, it becomes viscous, while its fluidity decreases and the internal friction resistance increases.
When the engine is cold, the oil must be thin enough so as not to overload the starter and so that it can reach all lubrication points as quickly as possible during the engine start. This requires the use of engine oil with a viscosity that changes as little as possible with temperature changes.
Fluidity or viscosity is equivalent to the internal friction of the oil and is designated by the SAE system (Society of Automobile Engineers), such as SAE 30, SAE 10, etc. High SAE numbers are thick oils, low numbers are thin oils. But viscosity does not at all characterize the lubricating properties of the oil.
Universal oil
Primera engine must use universal (all season) oils. All-season oils have the advantage of being adapted to temperature conditions (summer Winter). All-weather oils are made on the basis of liquid single-season oil (e.g. 15W). Thanks to the so-called thickener, the oil is stabilized when hot, so that its lubricating properties are maintained under all operating conditions. Letter "W" in the SAE designation means the suitability of the oil for operation in winter conditions.
Easy running oil
Light running oils are multigrade oils with added friction reducing agents that can provide up to 2 percent reduction in fuel consumption. Light running oils have a low viscosity (e.g. 10 W-30). They are based on unusual oils (synthetic oils). When buying an easy-stroke oil, make sure it is approved for use by NISSAN.
5W-20 engine oil is only suitable for very cold climates. Do not use on long high speed trips. For moderate climates, 10W-40 or 20W-50 engine oil is recommended.
Since the areas of application of neighboring SAE classes overlap, short-term temperature fluctuations can be ignored.
Engine oil specification
In principle, only HD oils are permitted for modern engines. HD oils are alloyed oils whose lubricating properties are greatly improved by the addition of various chemically active substances. These additives provide better anti-corrosion protection, better resistance to oxidation phenomena, especially reduction of the tendency to form crankcase deposits, improved viscosity stabilization, cleaning and dissolving properties. Cleaning and dissolving additives not only reduce the formation of deposits in the engine, but at the same time they have the ability to dissolve deposits and finely separate them and other contaminants in the engine and keep them in suspension, which makes it possible to drain all contaminants during an oil change.
The grade of HD oil is determined by the API system (API: American Petroleum Institute). European manufacturers also follow this system.
The designation consists of two letters. The first letter characterizes the range of application: S - Service, designed for gasoline engines, C - Commercial, designed for diesel engines.
The second letter indicates the variety in alphabetical order.
The highest grade are oils according to the CE API specification for diesel engines.
Attention! Engine oils that have a clear manufacturer's indication for use in diesel engines must not be used in gasoline or diesel engines. In this case, the double designation is indicated on the package (e.g. SF/ CD).
For Primera with diesel engines, engine oils are suitable - SD.
Oil consumption
For internal combustion engines, oil consumption refers to the consumption of the amount of oil that is consumed as a result of the combustion process. Oil consumption should not be confused with oil leakage due to leaks in the oil sump, cylinder head cover, etc.
Normal oil consumption occurs due to the combustion of small amounts of oil in the cylinders, due to the removal of combustion products and particles from friction. In addition, the oil is consumed due to the high temperatures and high pressures it is subjected to in the engine.
Further, oil consumption is influenced by operating conditions, driving style, as well as manufacturing tolerances. Oil consumption should be a maximum of 1.0 l/1000 km.