Do you know how the mechanism for opening your entrance or interior doors works? You probably know that everything is very simple there – a special device is attached to the wall, which is a pin, and a cylinder is attached to the door, the inner diameter of which is slightly larger, than the wall fastener. The pin goes into the door sleeve and voila – the door is able to move.
Doors creak and this problem is well known to all of us. Why is this happening? The thing is that the door cylinder and the wall pin are made of metal and, of course, as it turns, the door creates a frictional force in the hinge – one metal rubs against another. This causes the destruction of the metal, microchips and metal filings are formed. Moisture from the air enters the cylinder and the pin and causes oxidation. In winter, when the temperature is slightly lower, the cylinder diameter decreases, gripping the pin even more, and in summer, when the heat is in the air, the space between the pin and the cylinder, on the contrary, increases. All these constant dynamic changes affect the destruction of materials, their elastic properties, their chemical composition and strength characteristics.
How many times a day do you open and close the door? 10 times? 20? Maybe 50? Suppose you are a real fidget and open the door about 100 times a day. This means that you make 200 movements per day – once forward, the other time – back. When opening and closing the doors, the cylinder turns around the pin 90 + 90 = 180 degrees. So one turn of the door hinge is when you opened it twice and closed it twice. Go crazy and slam doors every day? Opened and closed the door 100 times? So, in fact, the loop performs 50 revolutions per day. This is approximately 2 full revolutions per hour, which means 0.03 revolutions per minute.
The crankshaft inside the engine makes 1,2,3 thousand revolutions per minute. Imagine if the rotation is 0.03 rpm. the doors are already starting to creak, what will happen to the crankshaft, which rotates … 65 thousand times faster! And if the door hinge should only withstand the weight of the door – 10, 15 kg, then the crankshaft is forced to set in motion a car weighing more than a ton and all its passengers!
The crankshaft is far from the only automotive unit that constantly moves and experiences an unprecedented load. Pistons with rings move in cylinders, valves (4 for each cylinder) knock like madmen in time with the piston, connecting rods set the crankshaft in motion, gears transfer newtons to shafts.
Even drawing such a simple analogy with interior door fasteners, it becomes obvious that oil in the engine is not just desirable, but necessary. Without it, the car will not work. Machine oil creates a viscous film on all metal surfaces and the parts stop rubbing against each other, as the oil creates a kind of thick cushion, taking on the load.
Thus, we can conclude that car oil protects the engine. This magic liquid not only lubricates its components, but also cleans the motor from debris and cools it. If, when changing the oil, we do not care about buying a product adapted to our car, then, without a doubt, we can expect an engine jam in the near future.
Before we start buying a new oil, we need to check in the car owner’s manual what the viscosity should be. It is this parameter that determines the internal friction of the particles of this oil, in other words, its density.
Immediately, I would like to note a few points:
The viscosity of the fluid should be selected in accordance with the recommendations of our vehicle manufacturer. This parameter is defined as follows. For example, let’s take 15W-40 oil, where 15 stands for winter viscosity and 40 for summer. In winter weather, the lower the number, the more fluid remains in the crankcase.
How can this be useful? Well, this value mainly affects engine ignition at low temperatures. If we buy an oil with a higher winter viscosity, we will have problems starting the engine in the cold, but we must remember that the fluid must adhere to the level indicated by the manufacturer in the operating instructions.
In the case of summer viscosity, the situation is as follows: the higher the viscosity, the more stable the oil density at higher temperatures. What does it mean? If we buy oil with a low summer viscosity, then we can expect that the fluid will lose its properties faster and, therefore, its level in the reservoir may decrease. As a result, we will be forced to change the oil to a new one, a little earlier than expected. But this is not scary, because this is how the motor works – what can you do.
As we have already proved, the most important of the parameters of a car oil is its viscosity. In simple language, understandable to the most ordinary driver who does not go deep into details, we can say that the viscosity of the oil is its ability to remain on the surface of the internal parts of the engine and at the same time maintain fluidity. It seems not difficult? But it is the viscosity of the oil that most of all changes depending on temperature, being a “variable” value?
So some sort of classification system is clearly needed. That is why the American Association of Automotive Engineers (SAE) has developed a viscosity classification of engine oil, which describes the viscosity of a particular motor oil at different operating temperatures. In fact, this classification gives the temperature range over which the engine is safe to operate, provided that the engine manufacturer has approved an engine oil with such parameters for use in this engine. Thus, if you have already decided to ignore the parting words of the manufacturer of your car and follow the advice of the professional Uncle Petit, then check for every fireman the compliance of this oil with the standard in the table.
What do the oil viscosity numbers on the label mean? We have already briefly written about this, but we will consider it in a little more detail.
After the SAE abbreviation, we see several numbers separated by the letter W and a dash, for example 5W-30 (for a multigrade oil, which, as a rule, all motorists use). Without going into physics and complex terminology (this is below), you can decipher this inscription as follows:
5W The decoding of the oil viscosity coding is a low-temperature viscosity, which means that a cold start of the engine is possible at a temperature not lower than -35 ° C (i.e. 40 must be subtracted from the number in front of W). This is the minimum temperature of this car oil, at which the engine oil pump can pump oil through the system, while preventing dry friction of internal parts. This parameter does not affect the operation of a warm engine.
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