In principle, viscosity describes the viscosity of liquids or gases. Water, for example, has a low viscosity because it is a thin liquid and therefore very flowing: at a temperature of 20 degrees, it has a viscosity of 1.
The colder a liquid, the more viscous it becomes; the warmer it is, the thinner it is. This is exactly what is so important with engine oil because it needs to be able to lubricate itself quickly during a cold start in both winter and summer, so you don’t have any engine damage.
On the other hand, the engine oil must not become too thin at high temperatures, so that the lubricating film in the engine does not break or the lubrication is not interrupted and high friction occurs.
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What is an SAE viscosity grade?
SAE is short for “Society of Automotive Engineers”. This organization determines which technical standards are valid for the automotive industry and manufacturers, including SAE viscosity classes.
Everyone knows this denomination from oil containers: for example SAE 5W30. In this case, the number 5 before the W describes the smoothness of the engine oil at low temperatures. The smaller the figure value here, the better the oil flow at low temperatures. The W stands for winter and indicates multigrade oils.
The number behind the W describes how well it lubricates engine oil when it is hot: The higher the value, the better the engine oil’s ability to maintain high-temperature lubrication in the engine.
According to the ADAC, it is even possible to save fuel when using the vehicle with so-called low-friction oils. The savings potential, however, depends on various factors such as the type of driving (diesel, petrol, gas, hybrid), the engine temperature, your driving style and of course the route profile.
For relatively new propulsion systems, such as hybrid technology, manufacturers are developing fully synthetic “hybrid oils” with very low viscosity levels from 0W-8 to 0W-20. As a general rule, when choosing engine oil, always use oil that meets your vehicle manufacturer’s specifications.
What is the ACEA specification?
ACEA is the acronym of “Association des Constructeurs Européens d’Automobiles” and in this association are organized 15 European manufacturers of cars, trucks and buses or manufacturers that produce for Europe, including BMW, Daimler, Fiat Chrysler, Honda, Renault, the Volkswagen Group, Toyota and Volvo.
In the ACEA classification, the engine and vehicle types for which the respective engine oil is intended are identified by letters: A stands for gasoline engines for passenger cars, B for diesel engines for passenger cars, vans and small transporters, C for gasoline engines and diesel for passenger cars with new exhaust gas after-treatment systems and E for diesel engines for trucks.
A combined presentation for petrol and diesel engines is, for example, ACEA A3 / B4. Here the additional figures indicate performance differences: In the example above, ACEA A3 / B4 marked engine oil will meet higher requirements than A1 / B1 oil.
What is the API classification?
The United States has its own quality classification for motor oils: API stands for “American Petroleum Institute”.
API S – the “S” stands for petrol engines
API C – the “C” stands for commercial vehicle diesel engines
The second letter (eg API SA) stands for the class (quality). The letter N denotes the highest performance class currently available for gasoline engines, while the A stands for additive-free motor oil, which today is only used for classic cars. In principle, the higher the letter of the alphabet, the better the quality through additives and additives:
API SB – oils with aging protection additives and anti-wear additives
API CD – heavy oils according to MIL 2104C (MIL ‑ L specification is an additional US military specification)
The API classification system is adapted to the vehicles on the American market and the driving conditions in that country, and it must be said at this point that this system can only be transferred to the engine oil qualities required in Europe to a limited extent, and that also Passenger car diesel engines are not classified by API.
What is the risk of the wrong oil for my car?
The engine depends on the lubricant and the lubricating film of the oil to run smoothly. If you choose an oil that is too thick or too thin for your vehicle, the lubrication will not work optimally. As a result, the metal surfaces of the engine components rub against each other so strongly that they can cause serious damage.
What happens if you put too much oil in the engine?
If too much oil has been poured into the engine, the pressure load will be too high and the seals may not be able to withstand it. It is also possible for bubbles to form in the oil. In the worst case, oil can leak at faulty seals or be drawn into the engine and burn. The result is engine damage.
Used oil can be delivered to regional recycling centers or to oil dealers and workshops, as they are obliged to collect the used oil. Important: Under no circumstances should it be mixed with other additives such as other used oils, brake fluid or solvents.
If too much oil has been added, there are two possibilities: If the max. on the dipstick is just passed, it shouldn’t be a problem to drive to the nearest garage. If, on the other hand, a lot more oil has been added to the engine than prescribed, it is best to leave the car stationary.
However, if this mishap happens to you in a workshop, because you do the maintenance yourself, the solution is simple: open the oil drain plug and collect the oil completely. Then you start refueling (but this time with the maximum amount of oil allowed).
Away from the workshop, you can also help yourself with an oil suction pump and a long hose, as long as you can use it to reach the oil pan.