Motorists know that choosing the right engine oil for their engine is critical. It is good when the manufacturer recommends a specific brand and type of oil. However, older car owners do not have this advantage. It is necessary to determine as precisely as possible the right engine oil so that the engine does not present surprises at the most inopportune moment. But there are so many markings on the oil cans. For example, 5w30 oil and 5w40 oil. What is the difference?
Definition
Oil 5w30 - engine oil, which is used to lubricate car engines. The oil designation contains two numbers that reflect the most important property of engine oil - viscosity at low and high temperatures. To start the engine at low temperatures, you need to choose an engine oil that should not be very viscous. And in summer, at high temperatures, oil, on the contrary, must keep a lubricating film between the parts. The first number in the designation "5w30" is the class of winter use (the letter "W", that is, "Winter", confirms this), the second number is the indicator of summer use. Thus, the oil is multigrade.
Oil 5w40 is a multigrade engine oil with a winter class of application - 5w, high temperature index - 40. These designations are adopted in the SAE (Society Automotive Engineers) and are the international standard for determining the viscosity of engine oils. Note that the viscosity-temperature characteristics of engine oils are paramount in determining quality.
Comparison
Engine oil is known to be composed of base oils and various thickening additives. It is these additives that give the desired effect in winter or summer. However, today, probably, to facilitate the work of a motorist, multigrade oils are more often used. The viscosity class of the engine oil depends on the quantity and quality of the thickening additives. In addition, this versatile oil changes its viscosity under the influence of shear rate. The lower the speed, the higher the viscosity.
The motor oils we are comparing today have different amounts of thickening agent. As a consequence, the second number - the viscosity behavior at high temperatures - is different. That is, 30 or 40 is an indicator of how long the engine oil is able to maintain a protective film when summer temperatures rise. This is a very important property for preserving the engine from premature wear and preventing the engine from stalling in the heat when in a traffic jam.
Conclusions TheDifference.ru
- Oil 5w40 with increasing temperatures in the summer has a higher viscosity than oil 5w30, which contributes to the smooth operation of the engine;
- At low temperatures, both 5w30 and 5w40 oil can be used down to -25 ° C.
