5W40
SAE 5W40 oil specification
The viscosity index is directly related to the temperature at which the oil can fully function. For use in temperate climates, oils are often selected that can work both in summer and in winter, and for cold regions, oils with reduced viscosity are suitable.
To determine the temperature regime of the technical fluid, the number 30-35 should be subtracted from the first digit of the SAE index, the resulting value will be the lower temperature limit. To derive the maximum limit of the plus temperature of the lubricant, it is necessary to subtract 5 from the second number of the index.
5W-40 is an all-season oil that must maintain fluidity at negative and positive temperatures within the established limits to be considered in this SAE tolerance class. SAE can be an indicator of the climate in which this oil can be used, only partially and only in relation to the low temperature indicator. In general, this is an indication of oil viscosity at different temperatures.
SAE 5W-40 viscosity indicators:
| Characteristics | Indexes | Details |
| Pumpability | -35℃ | The minimum temperature at which the oil is pumped through the channels |
| Pumpability | -30℃ | The minimum temperature at which the engine can be started. |
| Kinematic viscosity at 100 degrees | 12.6-16.3 mm2/s | The indicator must be within these limits so that the oil can be labeled 5W-40. |
| Kinematic viscosity at 40 degrees | 89-97 mm2/s | The same, but at a different temperature. This indicator is less important than viscosity at operating temperature. |
| Dynamic viscosity of CCS at -30 degrees | Not more than 6600 mPas | That is, the closer the indicator is to this limit, the worse the crankshaft will rotate even at -30 degrees. |
| Flash point | From 224℃ | It can be from +/- 10-15 degrees. |
| Freezing temperature | About -45℃ | It can be different. This indicator indicates the temperature at which the oil will completely freeze and cannot be pumped through the channels. |
It is clear from this table that the second two symbols in the marking 40 show what viscosity the oil will have exactly at the operating temperature, that is, it indicates the thickness of the oil film and how easily and quickly the oil will be pumped. It is very important to choose this indicator according to the manufacturer's recommendation, since different engines have different design features.
The first number 5 is an indication of low temperature viscosity, that is, at -30 ℃, the oil will retain enough fluidity to rotate the crankshaft.