Engine oil density. What parameters does it depend on?
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High Density Lubricants
The density of automotive oils varies at the level of 0,68–0,95 kg/l. Lubricants with an indicator above 0,95 kg / l are classified as high-density. These oils reduce mechanical stress in hydraulic transmission without loss of performance. However, due to the increased density, the lubricant does not penetrate into hard-to-reach areas of the piston cylinders. As a result: the load on the crank mechanism (crankshaft) increases. Lubricant consumption also increases and coke deposits form more often.
After 1,5–2 years, the lubricant is compacted by 4–7% of its original value, which indicates the need to replace the lubricant.
Low density motor oils
The decrease in the mass-volume parameter below 0,68 kg/l is due to the introduction of low-density impurities, for example, lightweight paraffins. Poor-quality lubricants in such a case lead to rapid wear of the hydromechanical elements of the engine, namely:
- The liquid does not have time to lubricate the surface of the moving mechanisms and flows into the crankcase.
- Increased burnout and coking on the metal parts of the internal combustion engine.
- Overheating of power mechanisms due to an increase in friction force.
- Increased lubricant consumption.
- Dirty oil filters.
Thus, for the correct operation of the “cylinder-piston” ligament, engine oil of optimal density is required. The value is determined for a specific engine type and is recommended according to SAE and API classifications.
Table of density of winter motor oils
Lubricants indicated by the index 5w40–25w40 are classified as winter types (W - Winter). The density of such products varies in the range of 0,85–0,9 kg/l. The number in front of the "W" indicates the temperature at which the piston cylinders are rotated and rotated. The second digit is the viscosity index of the heated liquid. The density index of the 5W40 class lubricant is the lowest among winter types - 0,85 kg / l at 5 ° C. A similar product of the 10W40 class has a value of 0,856 kg / l, and for 15w40 the parameter is 0,89–0,91 kg / l.
SAE engine oil grade | Density, kg/l |
5w30 | 0,865 |
5w40 | 0,867 |
10w30 | 0,865 |
10w40 | 0,865 |
15w40 | 0,910 |
20w50 | 0,872 |
Used engine oil density
After 1–2 years of use, the physical properties of technical lubricants deteriorate. The color of the product varies from light yellow to brown. The reason is the formation of decay products and the appearance of contaminants. Asphaltenes, carbene derivatives, as well as fireproof soot are the main components leading to the sealing of technical lubricants. For example, a 5w40 class liquid with a nominal value of 0,867 kg / l after 2 years has a value of 0,907 kg / l. It is impossible to eliminate the degradation chemical processes leading to a change in the density of engine oil.
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