# 10W-40, 5W-30, 5W-40, etc. How does this stand for?

10W-40, 5W-30, 5W-40, etc. How does this stand for?

• This designation in the form of the inscription 10W-30 on the package is the designation of the viscosity of the oil and its temperature regime. Usually these figures show an approximate permissible use of the motor operation in a certain temperature mode, for example:

10W-40 - temperature from -20 and up to + 40

20W-40 temperature from -10 and up to + 40.

• If your Oil is Written Letter W That This letter is a shortening from the word Winter (WINTER).

If 5W-30 is written on the oil, this means that the oil will work normally if the temperature is humming + 20 - -25 (5-30 = -25), (5-25 = -20).

If the letter W is not written on the oil, it means that the oil is not for winter, but for Summer!

In every case, I'll attach the scheme, where you will find under what temperature your Oil normally works.

In the picture you will find all types of oils, which work both in winter and in summer.

• Very many do not even suspect what those figures mean on the marking of engine oil. The figure before W is the maximum minus temperature of the outside air, at which the oil does not lose its properties, and it can be used, and hence the figure after this is the maximum plus temperature, which, by the way, determines the viscosity of the oil.

• If on the oil marking in this form 10W-40, for example, then you need to know how to decode the number before the letter W, and the last digit, because the first indicates the minimum negative temperature at which this oil can be used, and the last digit indicates the maximum temperature with a + sign.

## So, what do the numbers mean in the inscription 10W-40

There are markings: 0W, 5W, 10W, 15W, and 20W

• 0W - oil can be used at temperatures up to -35-30С
• 5W - oil can be used at temperatures up to -30-25С
• 10W - oil can be used at temperatures up to -25-20С
• 15W - oil can be used at temperatures up to -20-15С
• 20W - oil can be used at temperatures up to -15-10С

For the high-temperature viscosity, the following values ​​are possible: 30, 40, 50 and 60

• 30 - oil can be used at temperatures up to + 20-25С
• 40 - oil can be used at temperatures up to + 35-40С
• 50 - oil can be used at temperatures up to + 45-50С
• 60 - oil can be used at temperatures up to + 50С and above
• This designation of motor oils is used already from 1911 year, then a society of some kind of automobile engineers assembled there and decided to classify all the oils according to their applicability, this society was called - SAE (Society / Society / of Automotive / automotive / Engineers / engineers /).

So they took, and classified all the oils in viscosity, so that at first glance it was clear how and under what conditions it (oil) can be used.

Classification of this: SAE J300 includes 6 classes for the winter period and 5 classes for the summer period.

WINTER is lt; OW>, lt; 5W>, lt; 10W>, lt; 15W>, lt; 20W>, lt; 25W>.

SUMMER is lt; 20>, lt; 30>, lt; 40>, lt; 50>, lt; 60>.

Letter W is nothing short of a reduction from the winter in English Winter ...

So the numbers are the viscosity, the letter "; Wquot; - this is winter

The numbers to the left of the quotes are quot; Wquot; - designation for winter oil.

The numbers to the right of the letter "Wquot; - designation for summer oil.

If the figures are on both sides, the oil is considered all-weather for both winter and summer ...

The table shows at what temperatures, what oil can be used ...

• Consider the decoding of the oil marking using the example of 5W-30:

5W is an indicator of the ability of oil to resist low temperatures. It shows the minimum temperature at which a cold start of the engine is possible. If 5 is taken away from 40, then we get -35 degrees Celsius. This is the minimum temperature.

30 is an indicator that determines the viscosity of the oil at high engine operating temperatures. The higher the figure, the greater the kinematic viscosity of the oil.

The difference between the markings is that each oil is designed for use under certain climatic conditions and in a certain type of engine (gasoline or diesel, forced or not boosted, etc.).

• To explain the decoding, I'll take an example of 5W-40. And so this inscription is deciphered as follows:

• perform an arithmetic operation 5-40 = -35 is the minimum permissible temperature at which the oil pump pumps the oil through the system;
• now again take away 5-35 = -30 - this is the minimum temperature at which the engine will start;
• now we will reflect - the thicker the oil, the harder the starter and the battery, and therefore for the duration of the battery and starter it is more profitable to take the oil 0W-40;
• now we'll figure it out with a hot engine - no one knows exactly what temperatures in your engine, but the higher the temperatures withstand the better for the engine, the second number indicates what temperature the engine withstands oil, for marking 5W-40 it's from 100 to 150 degrees Celsius.
• that I do not understand, why is the summer temperature of the air? the second digits 30,40 ... mean the viscosity at the engine temperature from 100 to 150, and since there is a cooling system to preserve the engine temperature, which does not allow the engine to develop a temperature higher than the same 100 degrees, then there is nothing to do with the outside air temperature. And the fact that the numbers are the second difference 30,40, so this applies more to the thickness of the film at a certain engine temperature and gaps in the engine. for example, in Asian machines, the gaps between the piston and the cylinder are smaller, because the oil is mainly with the 30, since the viscosity is less, and the frictional resistance is less, and if you pour for example 5w40 and not 5w30, then naturally the frictional friction will be greater. but in Europe, oil viscosity is usually higher than 40 and so on.

• 10W-40, 5W-30, 5W-40 are designations for the specification of oils, and in particular their viscosity. The first figures before W speak about the viscosity of the oil in the winter, and the second figure in the summer (hot) period. For old cars, it is optimal to use 10W40 oil.

• Since in practice I did not need this to answer this question, I searched the Internet, and she also learned that all these markings mean, and here's a good table about this:

And here's a quote for you, explaining what qualities these brands show:

Here is the picture, which also shows the relationship between brands and air temperature:

I hope I was able to help you with decoding.