Engine oil (motor oil) for your car

Internal lubrication with oil the oil in an engine ensures reliable lubrication of all moving parts in an engine. In addition, the engine oil reliably dissipates friction heat. Incorrect, old or insufficient oil in an engine leads to a breakdown of the lubricating film. Then, major engine damage can occur very quickly. The path of engine oil The oil in an engine is pumped through a closed circuit. The oil is filled in at the valve cover. In the idle state, it runs off into the oil pan, which is located at the bottom of the engine. From there, the oil is drawn in and run through the engine's channels with pressure by the mechanical oil pump. It reaches all relevant points, up to the inside of the cylinder liners. Finally, it returns into the oil pan and the cycle repeats itself. Oil and viscosity The effect of lubricating oil depends on its flowability. The warmer the oil, the more fluid it is. Therefore, its viscosity is much higher in the cold state. However, this is not a huge issue for an engine: In the cold condition, the engine's metallic parts have contracted. The increase in free play keeps them from taking damage due to friction. The warmer the engine, the more its metal parts expand and friction increases. At the same time, the oil keeps getting more fluid, which in turn reduces friction. Thus, the engine is always optimally lubricated within its permitted temperature range. Types of engine oil Different classes of engine oil are available. The owner's manual specifies which type of engine oil is suitable for the vehicle. When it comes to lubricating oil, one can safely assume that "expensive is better". In particular, the oil's thermal behavior is very important: It should be as liquid as possible in the cold state, yet not too liquid when heated. This ensures optimum lubricity.
Engine oils can indeed be mixed, yet it is strongly recommended to always use the correct engine oil. Worse oil reduces the lubricity of high-quality oil.
Various distinguishing information can be found on the container. The most well-known is the so-called "W-number". This two number/letter combination provides information regarding the fluidity, the so-called "viscosity" of the oil. Even though there are over 200 different types of oil, the following markings are the most common:

- SAE 0W-40: can be used up to -40 °C, 12.5 mm²/s propagation speed (viscosity) at 100 °C - SAE 5W-40: can be used up to -35 °C, 12.5 mm²/s propagation speed (viscosity) at 100 °C - SAE 10W-60: can be used up to -30 °C, 21.9 mm²/s propagation speed (viscosity) at 100 °C - SAE 15W-40: up to -25 °C , 12.5 mm²/s propagation speed (viscosity) at 100 °C

The engine oil's cold start behavior is especially important at low temperatures. Vehicles commonly used at high RPM, such as motorcycles and sports cars, rely on very thin oil. Therefore, the oil should be chosen in accordance with the manufacturer's specifications. Depending on its viscosity, high-quality oil by a brand manufacturer (such as Castrol, Mobil or Liqui Moly) costs around 11 EUR per liter. Yet, one is sure to receive guaranteed maximum performance. Checking, refilling and changing engine oil The German automobile club recommends checking the oil level at every fuel stop. The oil level should always be between the minimum and the maximum, which are indicated by a stamping or a notch on the dipstick. Too much oil is even more harmful to the engine, than a level below the minimum. If oil needs to be refilled regularly, you should look for the cause of oil loss. Either there's an oil leak or it is being burned inside the engine compartment. In the latter case, the catalytic converter is at danger and can be destroyed by soot from the burning oil. When changing oil, the filter and the seal at the oil drain plug are also replaced. An oil change is particularly important after buying an older used car. One should definitely check the inside of the valve cover using a finger. If there's a layer of caked on oil, the cover should be removed, cleaned and reassembled with a fresh seal. Next, cheap oil is filled in and used for 100 kilometers, whereupon all of the engine oil is changed and the filter replaced according to the manufacturer's instructions. This can significantly increase an engine's lifespan.